cgroup-rts-threads (empty) → 0.1.0.0

raw patch · 12 files changed

+987/−0 lines, 12 filesdep +basedep +cgroup-rts-threadsdep +hspec-core

Dependencies added: base, cgroup-rts-threads, hspec-core, hspec-expectations, megaparsec, path, path-io, text

Files

• CHANGELOG.md +5/−0
• LICENSE +373/−0
• README.md +58/−0
• cgroup-rts-threads.cabal +71/−0
• src/Control/Concurrent/CGroup.hs +59/−0
• src/System/CGroup.hs +7/−0
• src/System/CGroup/CPU.hs +75/−0
• src/System/CGroup/Controller.hs +9/−0
• src/System/CGroup/Controller/Internal.hs +239/−0
• test/Main.hs +16/−0
• test/System/CGroup/CPUSpec.hs +23/−0
• test/System/CGroup/ControllerSpec.hs +52/−0

@@ -0,0 +1,5 @@+# Revision history for cgroup-rts-threads++## 0.1.0.0++- Initial release

@@ -0,0 +1,373 @@+Mozilla Public License Version 2.0+==================================++1. Definitions+--------------++1.1. "Contributor"+    means each individual or legal entity that creates, contributes to+    the creation of, or owns Covered Software.++1.2. "Contributor Version"+    means the combination of the Contributions of others (if any) used+    by a Contributor and that particular Contributor's Contribution.++1.3. "Contribution"+    means Covered Software of a particular Contributor.++1.4. "Covered Software"+    means Source Code Form to which the initial Contributor has attached+    the notice in Exhibit A, the Executable Form of such Source Code+    Form, and Modifications of such Source Code Form, in each case+    including portions thereof.++1.5. "Incompatible With Secondary Licenses"+    means++    (a) that the initial Contributor has attached the notice described+        in Exhibit B to the Covered Software; or++    (b) that the Covered Software was made available under the terms of+        version 1.1 or earlier of the License, but not also under the+        terms of a Secondary License.++1.6. "Executable Form"+    means any form of the work other than Source Code Form.++1.7. "Larger Work"+    means a work that combines Covered Software with other material, in+    a separate file or files, that is not Covered Software.++1.8. "License"+    means this document.++1.9. "Licensable"+    means having the right to grant, to the maximum extent possible,+    whether at the time of the initial grant or subsequently, any and+    all of the rights conveyed by this License.++1.10. "Modifications"+    means any of the following:++    (a) any file in Source Code Form that results from an addition to,+        deletion from, or modification of the contents of Covered+        Software; or++    (b) any new file in Source Code Form that contains any Covered+        Software.++1.11. "Patent Claims" of a Contributor+    means any patent claim(s), including without limitation, method,+    process, and apparatus claims, in any patent Licensable by such+    Contributor that would be infringed, but for the grant of the+    License, by the making, using, selling, offering for sale, having+    made, import, or transfer of either its Contributions or its+    Contributor Version.++1.12. "Secondary License"+    means either the GNU General Public License, Version 2.0, the GNU+    Lesser General Public License, Version 2.1, the GNU Affero General+    Public License, Version 3.0, or any later versions of those+    licenses.++1.13. "Source Code Form"+    means the form of the work preferred for making modifications.++1.14. "You" (or "Your")+    means an individual or a legal entity exercising rights under this+    License. For legal entities, "You" includes any entity that+    controls, is controlled by, or is under common control with You. For+    purposes of this definition, "control" means (a) the power, direct+    or indirect, to cause the direction or management of such entity,+    whether by contract or otherwise, or (b) ownership of more than+    fifty percent (50%) of the outstanding shares or beneficial+    ownership of such entity.++2. License Grants and Conditions+--------------------------------++2.1. Grants++Each Contributor hereby grants You a world-wide, royalty-free,+non-exclusive license:++(a) under intellectual property rights (other than patent or trademark)+    Licensable by such Contributor to use, reproduce, make available,+    modify, display, perform, distribute, and otherwise exploit its+    Contributions, either on an unmodified basis, with Modifications, or+    as part of a Larger Work; and++(b) under Patent Claims of such Contributor to make, use, sell, offer+    for sale, have made, import, and otherwise transfer either its+    Contributions or its Contributor Version.++2.2. Effective Date++The licenses granted in Section 2.1 with respect to any Contribution+become effective for each Contribution on the date the Contributor first+distributes such Contribution.++2.3. Limitations on Grant Scope++The licenses granted in this Section 2 are the only rights granted under+this License. No additional rights or licenses will be implied from the+distribution or licensing of Covered Software under this License.+Notwithstanding Section 2.1(b) above, no patent license is granted by a+Contributor:++(a) for any code that a Contributor has removed from Covered Software;+    or++(b) for infringements caused by: (i) Your and any other third party's+    modifications of Covered Software, or (ii) the combination of its+    Contributions with other software (except as part of its Contributor+    Version); or++(c) under Patent Claims infringed by Covered Software in the absence of+    its Contributions.++This License does not grant any rights in the trademarks, service marks,+or logos of any Contributor (except as may be necessary to comply with+the notice requirements in Section 3.4).++2.4. Subsequent Licenses++No Contributor makes additional grants as a result of Your choice to+distribute the Covered Software under a subsequent version of this+License (see Section 10.2) or under the terms of a Secondary License (if+permitted under the terms of Section 3.3).++2.5. Representation++Each Contributor represents that the Contributor believes its+Contributions are its original creation(s) or it has sufficient rights+to grant the rights to its Contributions conveyed by this License.++2.6. Fair Use++This License is not intended to limit any rights You have under+applicable copyright doctrines of fair use, fair dealing, or other+equivalents.++2.7. Conditions++Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted+in Section 2.1.++3. Responsibilities+-------------------++3.1. Distribution of Source Form++All distribution of Covered Software in Source Code Form, including any+Modifications that You create or to which You contribute, must be under+the terms of this License. You must inform recipients that the Source+Code Form of the Covered Software is governed by the terms of this+License, and how they can obtain a copy of this License. You may not+attempt to alter or restrict the recipients' rights in the Source Code+Form.++3.2. Distribution of Executable Form++If You distribute Covered Software in Executable Form then:++(a) such Covered Software must also be made available in Source Code+    Form, as described in Section 3.1, and You must inform recipients of+    the Executable Form how they can obtain a copy of such Source Code+    Form by reasonable means in a timely manner, at a charge no more+    than the cost of distribution to the recipient; and++(b) You may distribute such Executable Form under the terms of this+    License, or sublicense it under different terms, provided that the+    license for the Executable Form does not attempt to limit or alter+    the recipients' rights in the Source Code Form under this License.++3.3. Distribution of a Larger Work++You may create and distribute a Larger Work under terms of Your choice,+provided that You also comply with the requirements of this License for+the Covered Software. If the Larger Work is a combination of Covered+Software with a work governed by one or more Secondary Licenses, and the+Covered Software is not Incompatible With Secondary Licenses, this+License permits You to additionally distribute such Covered Software+under the terms of such Secondary License(s), so that the recipient of+the Larger Work may, at their option, further distribute the Covered+Software under the terms of either this License or such Secondary+License(s).++3.4. Notices++You may not remove or alter the substance of any license notices+(including copyright notices, patent notices, disclaimers of warranty,+or limitations of liability) contained within the Source Code Form of+the Covered Software, except that You may alter any license notices to+the extent required to remedy known factual inaccuracies.++3.5. Application of Additional Terms++You may choose to offer, and to charge a fee for, warranty, support,+indemnity or liability obligations to one or more recipients of Covered+Software. However, You may do so only on Your own behalf, and not on+behalf of any Contributor. You must make it absolutely clear that any+such warranty, support, indemnity, or liability obligation is offered by+You alone, and You hereby agree to indemnify every Contributor for any+liability incurred by such Contributor as a result of warranty, support,+indemnity or liability terms You offer. You may include additional+disclaimers of warranty and limitations of liability specific to any+jurisdiction.++4. Inability to Comply Due to Statute or Regulation+---------------------------------------------------++If it is impossible for You to comply with any of the terms of this+License with respect to some or all of the Covered Software due to+statute, judicial order, or regulation then You must: (a) comply with+the terms of this License to the maximum extent possible; and (b)+describe the limitations and the code they affect. Such description must+be placed in a text file included with all distributions of the Covered+Software under this License. Except to the extent prohibited by statute+or regulation, such description must be sufficiently detailed for a+recipient of ordinary skill to be able to understand it.++5. Termination+--------------++5.1. The rights granted under this License will terminate automatically+if You fail to comply with any of its terms. However, if You become+compliant, then the rights granted under this License from a particular+Contributor are reinstated (a) provisionally, unless and until such+Contributor explicitly and finally terminates Your grants, and (b) on an+ongoing basis, if such Contributor fails to notify You of the+non-compliance by some reasonable means prior to 60 days after You have+come back into compliance. Moreover, Your grants from a particular+Contributor are reinstated on an ongoing basis if such Contributor+notifies You of the non-compliance by some reasonable means, this is the+first time You have received notice of non-compliance with this License+from such Contributor, and You become compliant prior to 30 days after+Your receipt of the notice.++5.2. If You initiate litigation against any entity by asserting a patent+infringement claim (excluding declaratory judgment actions,+counter-claims, and cross-claims) alleging that a Contributor Version+directly or indirectly infringes any patent, then the rights granted to+You by any and all Contributors for the Covered Software under Section+2.1 of this License shall terminate.++5.3. In the event of termination under Sections 5.1 or 5.2 above, all+end user license agreements (excluding distributors and resellers) which+have been validly granted by You or Your distributors under this License+prior to termination shall survive termination.++************************************************************************+*                                                                      *+*  6. Disclaimer of Warranty                                           *+*  -------------------------                                           *+*                                                                      *+*  Covered Software is provided under this License on an "as is"       *+*  basis, without warranty of any kind, either expressed, implied, or  *+*  statutory, including, without limitation, warranties that the       *+*  Covered Software is free of defects, merchantable, fit for a        *+*  particular purpose or non-infringing. The entire risk as to the     *+*  quality and performance of the Covered Software is with You.        *+*  Should any Covered Software prove defective in any respect, You     *+*  (not any Contributor) assume the cost of any necessary servicing,   *+*  repair, or correction. This disclaimer of warranty constitutes an   *+*  essential part of this License. No use of any Covered Software is   *+*  authorized under this License except under this disclaimer.         *+*                                                                      *+************************************************************************++************************************************************************+*                                                                      *+*  7. Limitation of Liability                                          *+*  --------------------------                                          *+*                                                                      *+*  Under no circumstances and under no legal theory, whether tort      *+*  (including negligence), contract, or otherwise, shall any           *+*  Contributor, or anyone who distributes Covered Software as          *+*  permitted above, be liable to You for any direct, indirect,         *+*  special, incidental, or consequential damages of any character      *+*  including, without limitation, damages for lost profits, loss of    *+*  goodwill, work stoppage, computer failure or malfunction, or any    *+*  and all other commercial damages or losses, even if such party      *+*  shall have been informed of the possibility of such damages. This   *+*  limitation of liability shall not apply to liability for death or   *+*  personal injury resulting from such party's negligence to the       *+*  extent applicable law prohibits such limitation. Some               *+*  jurisdictions do not allow the exclusion or limitation of           *+*  incidental or consequential damages, so this exclusion and          *+*  limitation may not apply to You.                                    *+*                                                                      *+************************************************************************++8. Litigation+-------------++Any litigation relating to this License may be brought only in the+courts of a jurisdiction where the defendant maintains its principal+place of business and such litigation shall be governed by laws of that+jurisdiction, without reference to its conflict-of-law provisions.+Nothing in this Section shall prevent a party's ability to bring+cross-claims or counter-claims.++9. Miscellaneous+----------------++This License represents the complete agreement concerning the subject+matter hereof. If any provision of this License is held to be+unenforceable, such provision shall be reformed only to the extent+necessary to make it enforceable. Any law or regulation which provides+that the language of a contract shall be construed against the drafter+shall not be used to construe this License against a Contributor.++10. Versions of the License+---------------------------++10.1. New Versions++Mozilla Foundation is the license steward. Except as provided in Section+10.3, no one other than the license steward has the right to modify or+publish new versions of this License. Each version will be given a+distinguishing version number.++10.2. Effect of New Versions++You may distribute the Covered Software under the terms of the version+of the License under which You originally received the Covered Software,+or under the terms of any subsequent version published by the license+steward.++10.3. Modified Versions++If you create software not governed by this License, and you want to+create a new license for such software, you may create and use a+modified version of this License if you rename the license and remove+any references to the name of the license steward (except to note that+such modified license differs from this License).++10.4. Distributing Source Code Form that is Incompatible With Secondary+Licenses++If You choose to distribute Source Code Form that is Incompatible With+Secondary Licenses under the terms of this version of the License, the+notice described in Exhibit B of this License must be attached.++Exhibit A - Source Code Form License Notice+-------------------------------------------++  This Source Code Form is subject to the terms of the Mozilla Public+  License, v. 2.0. If a copy of the MPL was not distributed with this+  file, You can obtain one at http://mozilla.org/MPL/2.0/.++If it is not possible or desirable to put the notice in a particular+file, then You may include the notice in a location (such as a LICENSE+file in a relevant directory) where a recipient would be likely to look+for such a notice.++You may add additional accurate notices of copyright ownership.++Exhibit B - "Incompatible With Secondary Licenses" Notice+---------------------------------------------------------++  This Source Code Form is "Incompatible With Secondary Licenses", as+  defined by the Mozilla Public License, v. 2.0.

@@ -0,0 +1,58 @@+# cgroup-rts-threads++![Hackage](https://img.shields.io/hackage/v/cgroup-rts-threads)+![tests](https://github.com/cnr/cgroup-rts-threads/actions/workflows/tests.yml/badge.svg)++This library provides a container-/cgroup-aware substitute for GHC's [RTS `-N` flag][rts-n], used to set the number of runtime threads.++Similar to the RTS `-N` flag, this library considers the number of cpu cores (as reported by `GHC.Conc.getNumProcessors`) to set this number.++Unlike the RTS `-N` flag, this library observes the process' [cgroup cpu quota][cgroup-quota] to constrain the number of runtime threads, as applicable.++When running outside of a cgroup, or on a platform other than linux, this library matches the behavior of `-N`.++See the [Why?](#why) section for details.++## Usage++1. Remove `-N` from your executable's `rtsopts`. In `yourproject.cabal`:++```cabal-config+-- before+executable my-executable+  ghc-options: -threaded -with-rtsopts=-N++-- after+executable my-executable+  ghc-options: -threaded+```++2. In your program's `main` function, call `initRTSThreads`:++```haskell+module Main (main) where++import Control.Concurrent.CGroup (initRTSThreads)++main :: IO ()+main = do+  initRTSThreads+  [...]+```++## Why?++It's common in containerized environments to limit cpu consumption of individual containers. There are two primary ways of doing this:++1. The `cpuset` option within a cgroup, which can be used to pin a process to specific cpu cores.+2. The `cfs.cpu_quota_us` option within a cgroup, which can be used to set a limit on the cpu time a process is allowed to consume.++The GHC threaded RTS offers [a flag, `-N`,][rts-n] that can be used to automatically determine the number of threads to use, based on the number of physical processors.++The RTS `-N` flag, [as of GHC `9.0.1`][cpuset-commit], respects the `cpuset` option when automatically determining the number of threads to use.++Unfortunately, the RTS `-N` flag **does not respect cgroup `cfs` quotas**. This leads to substantially degraded performance when there's a large disparity between a `cfs` quota and the number of physical cpu cores -- a very common scenario in, e.g., production kubernetes clusters.++[cpuset-commit]: https://gitlab.haskell.org/ghc/ghc/-/commit/4413828b7c507872c56719fb8920e1c2322830f8+[rts-n]: https://downloads.haskell.org/~ghc/9.0.1/docs/html/users_guide/using-concurrent.html#rts-options-for-smp-parallelism+[cgroup-quota]: https://www.kernel.org/doc/html/latest/scheduler/sched-bwc.html#management

@@ -0,0 +1,71 @@+cabal-version:      3.0+name:               cgroup-rts-threads+version:            0.1.0.0+synopsis:+  A container-/cgroup-aware substitute for the GHC RTS `-N` flag++description:+  This library provides a container-/cgroup-aware substitute for the GHC RTS+  `-N` flag. See the README for details.++homepage:           https://github.com/cnr/cgroup-rts-threads+bug-reports:        https://github.com/cnr/cgroup-rts-threads/issues+license:            MPL-2.0+license-file:       LICENSE+category:           Concurrency+author:             Connor James+maintainer:         connornjames@gmail.com+extra-source-files:+  CHANGELOG.md+  README.md++source-repository head+  type:     git+  location: https://github.com/cnr/cgroup-rts-threads.git++common lang+  default-language:   Haskell2010+  default-extensions:+    OverloadedStrings+    ScopedTypeVariables++  ghc-options:+    -Wall -Wincomplete-uni-patterns -Wcompat+    -Wincomplete-record-updates -Wmissing-home-modules+    -Wmissing-export-lists -Wredundant-constraints++library+  import:          lang++  -- cabal-fmt: expand src+  exposed-modules:+    Control.Concurrent.CGroup+    System.CGroup+    System.CGroup.CPU+    System.CGroup.Controller+    System.CGroup.Controller.Internal++  build-depends:+    , base        >=4.13 && <5+    , megaparsec  >=8    && <10+    , path        >=0.7  && <0.10+    , text++  hs-source-dirs:  src++test-suite test+  import:         lang+  type:           exitcode-stdio-1.0+  hs-source-dirs: test+  main-is:        Main.hs+  other-modules:+    System.CGroup.CPUSpec+    System.CGroup.ControllerSpec++  build-depends:+    , base+    , cgroup-rts-threads+    , hspec-core          ^>=2.8.3+    , hspec-expectations  ^>=0.8.2+    , path+    , path-io

@@ -0,0 +1,59 @@+-- | This module provides a container-/cgroup-aware substitute for GHC's RTS+-- @-N@ flag. See 'initRTSThreads'.+module Control.Concurrent.CGroup (+  initRTSThreads,+) where++import Control.Exception (Exception (..), SomeAsyncException (SomeAsyncException), SomeException, catch, throwIO)+import GHC.Conc (getNumProcessors, setNumCapabilities)+import System.CGroup.CPU (CPUQuota (..), getCPUQuota, resolveCPUController)++-- | A container-/cgroup-aware substitute for GHC's RTS @-N@ flag.+--+-- On most platforms, this sets the number of runtime threads to match the+-- number of physical processors (see 'GHC.Conc.getNumProcessors'), which is the+-- default behavior of the GHC @-N@ flag.+--+-- When running within a cgroup on linux (most often within a container), this+-- observes the current process' cgroup cpu quota to constrain the number of+-- runtime threads.+--+-- See 'CPUQuota'+initRTSThreads :: IO ()+initRTSThreads =+  initRTSThreadsFromCGroup+    `safeCatch` (\(_ :: SomeException) -> defaultInitRTSThreads)++-- | Uses the current process' cgroup cpu quota to set the number of runtime+-- threads.+--+-- Throws an Exception when the current process is not running within a cgroup.+initRTSThreadsFromCGroup :: IO ()+initRTSThreadsFromCGroup = do+  cpuController <- resolveCPUController+  cgroupCpuQuota <- getCPUQuota cpuController+  case cgroupCpuQuota of+    NoQuota -> defaultInitRTSThreads+    CPUQuota quota period -> do+      procs <- getNumProcessors+      let capabilities = clamp 1 procs (quota `div` period)+      setNumCapabilities capabilities++-- | Set number of runtime threads to the number of available processors. This+-- matches the behavior of GHC's RTS @-N@ flag.+defaultInitRTSThreads :: IO ()+defaultInitRTSThreads = setNumCapabilities =<< getNumProcessors++-- | Clamp a value within a range+clamp :: Int -> Int -> Int -> Int+clamp lower upper = max lower . min upper++-- | Catch non-async exceptions+safeCatch :: Exception e => IO a -> (e -> IO a) -> IO a+safeCatch act hdl = act `catch` (\e -> if isSyncException e then hdl e else throwIO e)++isSyncException :: Exception e => e -> Bool+isSyncException e =+  case fromException (toException e) of+    Just (SomeAsyncException _) -> False+    Nothing -> True

@@ -0,0 +1,7 @@+-- | CGroup controller types and operations (re-exported from System.CGroup.*)+module System.CGroup (+  module X,+) where++import System.CGroup.CPU as X+import System.CGroup.Controller as X

@@ -0,0 +1,75 @@+{-# LANGUAGE TemplateHaskell #-}++-- | Types and operations for the CPU CGroup controller.+module System.CGroup.CPU (+  -- * The CPU cgroup controller+  CPU,+  resolveCPUController,++  -- * Operations on the CPU controller+  CPUQuota (..),+  getCPUQuota,+) where++import Control.Monad ((<=<))+import Path+import System.CGroup.Controller (Controller (..), resolveCGroupController)++-- | The "cpu" cgroup controller+data CPU++-- | Resolve the CPU cgroup controller for the current process+--+-- Throws an Exception if the CPU controller is not able to be found, or when+-- running outside of a cgroup+resolveCPUController :: IO (Controller CPU)+resolveCPUController = resolveCGroupController "cpu"++-- | A CPU quota is the amount of CPU time our process can use relative to the+-- scheduler period+--+-- For example:+--+-- @+-- | cpu.cfs_quota_us | cpu.cfs_period_us | description |+-- | ---------------- | ----------------- | ----------- |+-- |           100000 |            100000 | (1)         |+-- |           200000 |            100000 | (2)         |+-- |            50000 |            100000 | (3)         |+-- |               -1 |            100000 | (4)         |+-- @+--+-- (1): we can use up to a single CPU core+--+-- (2): we can use up to two CPU cores+--+-- (3): the scheduler will give us a single CPU core for up to 50% of the time+--+-- (4): we can use all available CPU resources (there is no quota)+data CPUQuota+  = NoQuota+  | -- | cpu.cfs_quota_us, cpu.cfs_period_us+    CPUQuota Int Int+  deriving (Eq, Ord, Show)++-- | Read a CGroup configuration value from its file+readCGroupInt :: Path b File -> IO Int+readCGroupInt = readIO <=< (readFile . toFilePath)++-- | Get the CPU quota within the given cgroup CPU controller+getCPUQuota :: Controller CPU -> IO CPUQuota+getCPUQuota (Controller root) = do+  quota <- readCGroupInt (root </> cpuQuotaPath)+  case quota of+    (-1) -> pure NoQuota+    _ -> CPUQuota quota <$> readCGroupInt (root </> cpuPeriodPath)++-- Path to the "cpu quota" file+--+-- When this file contains "-1", there is no quota set+cpuQuotaPath :: Path Rel File+cpuQuotaPath = $(mkRelFile "cpu.cfs_quota_us")++-- Path to the "cpu period" file+cpuPeriodPath :: Path Rel File+cpuPeriodPath = $(mkRelFile "cpu.cfs_period_us")

@@ -0,0 +1,9 @@+-- | Common types and operations for CGroup controllers.+module System.CGroup.Controller (+  -- * CGroup Controllers+  Controller (..),+  resolveCGroupController,+  resolveCGroupController',+) where++import System.CGroup.Controller.Internal (Controller (..), resolveCGroupController, resolveCGroupController')

@@ -0,0 +1,239 @@+-- | Internal types and functions for cgroup controllers+module System.CGroup.Controller.Internal (+  -- * CGroup Controllers+  Controller (..),+  resolveCGroupController,+  resolveCGroupController',++  -- * CGroups+  CGroup (..),++  -- * Mounts+  Mount (..),++  -- * Internal intermediate operations+  findMatchingCGroup,+  resolveControllerMountPath,+  tryResolveMount,+  parseMountInfo,+  parseCGroups,+  Parser,+) where++import Control.Exception (throwIO)+import Control.Monad (guard)+import Data.Char (isSpace)+import Data.Foldable (find)+import Data.Maybe (listToMaybe, mapMaybe)+import Data.Text (Text)+import qualified Data.Text as Text+import qualified Data.Text.IO as TIO+import Data.Void (Void)+import Path+import Text.Megaparsec (Parsec, eof, manyTill, optional, parse, skipMany, some, takeWhile1P, takeWhileP)+import Text.Megaparsec.Char (char)+import qualified Text.Megaparsec.Char.Lexer as L++-- | A CGroup controller path for a specific subsystem+newtype Controller a = Controller {unController :: Path Abs Dir}+  deriving (Eq, Ord, Show)++-- | Resolve a CGroup controller by name, as viewed by the current process+--+-- see cgroups(7): \/proc\/self\/cgroup is a file that contains information about+-- control groups applied to this process+--+-- see proc(5): \/proc\/self\/mountinfo is a file that contains information about+-- mounts available to this process+--+-- Throws an Exception when the controller is not able to be found, or when+-- running outside of a cgroup+resolveCGroupController :: Text -> IO (Controller a)+resolveCGroupController controller = do+  cgroupPath <- parseAbsFile "/proc/self/cgroup"+  mountinfoPath <- parseAbsFile "/proc/self/mountinfo"+  resolveCGroupController' cgroupPath mountinfoPath controller++-- | Resolve a CGroup controller by name, under the given cgroup and+-- mountinfo paths+--+-- Throws an Exception when the controller is not able to be found, or when+-- running outside of a cgroup+resolveCGroupController' :: Path Abs File -> Path Abs File -> Text -> IO (Controller a)+resolveCGroupController' cgroupPath mountinfoPath controllerName = do+  cgroups <- parseFile parseCGroups cgroupPath+  mounts <- parseFile parseMountInfo mountinfoPath+  cgroup <- maybe (fail "Couldn't find cgroup for controller") pure (findMatchingCGroup controllerName cgroups)+  resolved <- maybe (fail "Couldn't find mount for cgroup") pure (resolveControllerMountPath controllerName cgroup mounts)++  pure (Controller resolved)++-- | Parse a file+parseFile :: Parser a -> Path b File -> IO a+parseFile parser file = either throwIO pure . parse parser (toFilePath file) =<< TIO.readFile (toFilePath file)++-- | Find a CGroup matching a controller name+--+-- For cgroups version 1, we use @containsController@ to explicitly look for the controller within a cgroup+--+-- For cgroups version 2, we use @emptyControllers@ to find a cgroup without any controllers+--+-- see cgroups(7): \/proc\/[pid]\/cgroup section+findMatchingCGroup :: Text -> [CGroup] -> Maybe CGroup+findMatchingCGroup controllerName = find (\group -> containsController group || emptyControllers group)+  where+    containsController :: CGroup -> Bool+    containsController = (controllerName `elem`) . controlGroupControllers++    emptyControllers :: CGroup -> Bool+    emptyControllers = null . controlGroupControllers++-- | Find a Mount matching a controller name and cgroup, returning the absolute+-- resolved path of a controller+resolveControllerMountPath :: Text -> CGroup -> [Mount] -> Maybe (Path Abs Dir)+resolveControllerMountPath controllerName cgroup = firstMaybe (tryResolveMount controllerName cgroup)++firstMaybe :: (a -> Maybe b) -> [a] -> Maybe b+firstMaybe f = listToMaybe . mapMaybe f++-- | Attempt to match a cgroup controller to a mount, returning the absolute+-- resolved path of the controller+--+-- Returns Nothing if the mount does not match the cgroup controller+--+-- A matching mount must have a filesystem type of "cgroup" and contain the+-- controller name within its "super options".+--+-- Per cgroups(7), the cgroup path is relative to a mount root in the process's+-- mount hierarchy. Notably, a mount root /is not the same as its mount point/.+-- A mount point is the path at which the mount is visible to the process.+--+-- As such, we need to look for a mount whose mount root either..+--+-- - ..exactly matches our cgroup's path, in which case we directly return the+--   mount's mount path; OR+--+-- - ..is a prefix of our cgroup's path, in which case we return the relative+--   path from the mount root appended to the mount's mount path+tryResolveMount :: Text -> CGroup -> Mount -> Maybe (Path Abs Dir)+tryResolveMount controllerName cgroup mount = do+  guard ("cgroup" == mountFilesystemType mount)+  guard (controllerName `elem` mountSuperOptions mount)+  if controlGroupPath cgroup == mountRoot mount+    then Just (mountPoint mount)+    else do+      rel <- stripProperPrefix (mountRoot mount) (controlGroupPath cgroup)+      Just (mountPoint mount </> rel)++-----++-- | A cgroup, as viewed within \/proc\/[pid]\/cgroup+--+-- see cgroups(7): \/proc\/[pid]\/cgroup section+data CGroup = CGroup+  { controlGroupControllers :: [Text]+  , controlGroupPath :: Path Abs Dir+  }+  deriving (Show)++-- | Parse an entire \/proc\/[pid]\/cgroup file into a list of cgroups+parseCGroups :: Parser [CGroup]+parseCGroups = some parseSingleCGroup <* eof++-- | Parse a single cgroup line within \/proc\/[pid]\/cgroup+--+-- hierarchyID:list,of,controllers:path+--+-- In cgroups version 1, a comma-separated list of controllers exists within each group+--+-- In cgroups version 2, the "controllers" section is always an empty string+--+-- see cgroups(7): \/proc\/[pid]\/cgroup section+parseSingleCGroup :: Parser CGroup+parseSingleCGroup =+  CGroup+    <$ takeUntil1P ':' -- ignore hierarchy ID number+    <*> (splitOnIgnoreEmpty "," <$> takeUntilP ':') -- comma-separated list of controllers+    <*> (parseIntoAbsDir =<< takeUntil1P '\n') -- path++-- return the prefix of the input until reaching the supplied character.+-- the character is also consumed as part of this parser.+--+-- this parser succeeds even when the character does not exist in the input+takeUntilP :: Char -> Parser Text+takeUntilP c = takeWhileP Nothing (/= c) <* optional (char c)++-- like 'takeUntilP', but expects a non-empty prefix before the character+takeUntil1P :: Char -> Parser Text+takeUntil1P c = takeWhile1P Nothing (/= c) <* optional (char c)++-- Data.Text.splitOn, but returns empty list on empty haystack, rather than [""]+--+-- >>> Data.Text.splitOn "foo" ""+-- [""]+--+-- >>> splitOnIgnoreEmpty "foo" ""+-- []+splitOnIgnoreEmpty :: Text -> Text -> [Text]+splitOnIgnoreEmpty _ "" = []+splitOnIgnoreEmpty s str = Text.splitOn s str++--------------++-- | A mount, as viewed within \/proc\/[pid]\/mountinfo+--+-- see proc(5): \/proc\/[pid]\/mountinfo section+data Mount = Mount+  { mountId :: Text+  , mountParentId :: Text+  , mountStDev :: Text+  , mountRoot :: Path Abs Dir+  , mountPoint :: Path Abs Dir+  , mountOptions :: Text+  , mountTags :: [Text]+  , mountFilesystemType :: Text+  , mountSource :: Text+  , mountSuperOptions :: [Text]+  }+  deriving (Show)++-- | Parse an entire \/proc\/[pid]\/mountinfo file into a list of mounts+parseMountInfo :: Parser [Mount]+parseMountInfo = some parseSingleMount <* eof++-- | Parse a single mount line within \/proc\/[pid]\/mountinfo+--+-- Fields are space-separated+--+-- see proc(5): \/proc\/[pid]\/mountinfo section+parseSingleMount :: Parser Mount+parseSingleMount =+  Mount+    <$> field -- id+    <*> field -- parent id+    <*> field -- st_dev+    <*> (parseIntoAbsDir =<< field) -- mount root+    <*> (parseIntoAbsDir =<< field) -- mount point+    <*> field -- mount options+    <*> field `manyTill` separator -- optional mount tags, terminated by "-"+    <*> field -- filesystem type+    <*> field -- mount source+    <*> (splitOnIgnoreEmpty "," <$> field) -- super options+    <* optional (char '\n')++-- | Megaparsec Parser+type Parser = Parsec Void Text++-- a field in the mountinfo file, terminated by whitespace+field :: Parser Text+field = lexeme $ takeWhile1P Nothing (not . isSpace)++-- separator after optional mount tags ("-")+separator :: Parser Char+separator = lexeme $ char '-'++lexeme :: Parser a -> Parser a+lexeme = L.lexeme (skipMany (char ' '))++parseIntoAbsDir :: Text -> Parser (Path Abs Dir)+parseIntoAbsDir = either (fail . show) pure . parseAbsDir . Text.unpack

@@ -0,0 +1,16 @@+module Main (+  main,+) where++import qualified System.CGroup.CPUSpec as CPUSpec+import qualified System.CGroup.ControllerSpec as ControllerSpec+import Test.Hspec.Core.Runner (hspec)+import Test.Hspec.Core.Spec (Spec)++main :: IO ()+main = hspec tests++tests :: Spec+tests = do+  CPUSpec.tests+  ControllerSpec.tests

@@ -0,0 +1,23 @@+module System.CGroup.CPUSpec (+  tests,+) where++import Control.Monad.IO.Class (liftIO)+import Path.IO (resolveDir')+import System.CGroup.CPU+import System.CGroup.Controller (Controller (..))+import Test.Hspec.Core.Spec (Spec, describe, it)+import Test.Hspec.Expectations (shouldBe)++tests :: Spec+tests = do+  describe "getCPUQuota" $ do+    it "should return CPUQuota when there is a quota" $ do+      controller <- resolveDir' "test/System/CGroup/testdata-cpu/quota"+      quota <- liftIO $ getCPUQuota (Controller controller)+      quota `shouldBe` CPUQuota 1 2++    it "should return NoQuota when there is no quota" $ do+      controller <- resolveDir' "test/System/CGroup/testdata-cpu/noquota"+      quota <- liftIO $ getCPUQuota (Controller controller)+      quota `shouldBe` NoQuota

@@ -0,0 +1,52 @@+module System.CGroup.ControllerSpec (+  tests,+) where++import Control.Monad.IO.Class (liftIO)+import Path+import Path.IO (resolveFile')+import System.CGroup.Controller+import System.Info (os)+import Test.Hspec.Core.Spec (Spec, describe, it)+import Test.Hspec.Expectations (shouldBe)++-- This test won't work on Windows, because paths starting with `/` are invalid+tests :: Spec+tests = exceptOnWindows $ do+  describe "resolveGroupController" $ do+    it "should work on a real world example" $ do+      cgroup <- resolveFile' "test/System/CGroup/testdata-controller/realworld/cgroup"+      mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/realworld/mountinfo"+      expected <- parseAbsDir "/sys/fs/cgroup/cpu"++      controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu"+      controller `shouldBe` Controller expected++    it "should resolve a direct mount root" $ do+      cgroup <- resolveFile' "test/System/CGroup/testdata-controller/direct/cgroup"+      mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/direct/mountinfo"+      expected <- parseAbsDir "/sys/fs/cgroup/cpu"++      controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu"+      controller `shouldBe` Controller expected++    it "should resolve subdirectories of a mount root" $ do+      cgroup <- resolveFile' "test/System/CGroup/testdata-controller/indirect/cgroup"+      mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/indirect/mountinfo"+      expected <- parseAbsDir "/sys/fs/cgroup/cpu/subdir"++      controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu"+      controller `shouldBe` Controller expected++    it "should work for cgroups v2" $ do+      cgroup <- resolveFile' "test/System/CGroup/testdata-controller/cgroupsv2/cgroup"+      mountinfo <- resolveFile' "test/System/CGroup/testdata-controller/cgroupsv2/mountinfo"+      expected <- parseAbsDir "/sys/fs/cgroup/cpu"++      controller <- liftIO $ resolveCGroupController' cgroup mountinfo "cpu"+      controller `shouldBe` Controller expected++exceptOnWindows :: Applicative f => f () -> f ()+exceptOnWindows act+  | os == "mingw32" = pure ()+  | otherwise = act