eventlog2html-0.11.0: inline-docs/heap.html

<dl>
  <dt style="color: red">Heap Size</dt>
  <dd>Total size of <emph>megablocks</emph> allocated by the RTS</dd>
  <dt style="color: blue">Blocks Size</dt>
  <dd>Total size of <emph>blocks</emph> allocated by the RTS</dd>
  <dt style="color: green">Live bytes</dt>
  <dd>Total size of objects live on the heap (should match top of area pane)</dd>
</dl>

<p>Process memory usage (as reported by the OS) should correspond roughly to the <span style="color: red">heap size</span>,
except for data allocated through the FFI (and the RTS also calls <tt>malloc()</tt> itself in a few places).
</p>

<p>
When heap profiling is enabled, <span style="color: blue">blocks
size</span> and <span style="color: green">live bytes</span>
will typically differ by the size of the nursery.
For understanding the relationship between <span style="color: blue">blocks
size</span> and <span style="color: green">live bytes</span>,
this <a href="https://www.well-typed.com/blog/2021/03/memory-return/">blog
post</a> contains more information.</p>

<p>
When heap profiling is not enabled, <span style="color: green">live bytes</span> will be updated only on a major GC, but <span style="color: red">heap size</span> and <span style="color: blue">blocks size</span> are updated more frequently. (Enabling heap profiling causes more frequent major GCs to collect heap samples.)
</p>

<p>
This view can also be useful in identifying
fragmentation. A very badly fragmented heap will have low <span style="color: green">live bytes</span> but
much higher <span style="color: blue">blocks size</span>.
</p>