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41 lines
1.6 KiB
Markdown
41 lines
1.6 KiB
Markdown
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# Vendored mimalloc
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This is [mimalloc](https://github.com/microsoft/mimalloc) vendored for use in
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our server code. You can upgrade mimalloc by editing `VERSION` in
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`update-sources.sh` and re-running it.
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Usage sites in haskell projects look like:
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-- See 'preload-mimalloc/README.md'
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-- We want this in all server binary executable sections
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common preload-mimalloc
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c-sources: ../preload-mimalloc/mimalloc/src/static.c
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include-dirs: ../preload-mimalloc/mimalloc/include
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cc-options: -DMI_MALLOC_OVERRIDE
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## Usage in haskell projects
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In [#9447](https://github.com/hasura/graphql-engine-mono/pull/9447) we see
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overloading the server with large and slow queries results in high memory usage
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and what looks like a space leak, involving foreign data from libpq.
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See that ticket for details, but mimalloc helps (relative to my glibc) by:
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- better avoiding fragmentation, resulting in lower overall memory usage (4GB peak 2.8 aftervs.
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- eagerly decomitting memory so that OS-reported memory usage is a useful
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metric (we do the same in the haskell RTS by specifying
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`--disable-delayed-os-memory-return`)
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We also benefit by standardizing this, rather than relying on users' glibc
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version, which might vary in behavior, making debugging difficult.
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Other implementations such as tcmalloc or jemalloc were not tested but might
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perform better or be more tunable.
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### Why not LD_PRELOAD?
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It's most common and simplest to use the dynamic linker to override malloc.
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This would work in docker containers we ship, but we want all users to have the
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same (better) behavior out of the box.
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