Paul Hauner 456b313665 Tune GNU malloc (#2299) ... ## Issue Addressed NA ## Proposed Changes Modify the configuration of [GNU malloc](https://www.gnu.org/software/libc/manual/html_node/The-GNU-Allocator.html) to reduce memory footprint. - Set `M_ARENA_MAX` to 4. - This reduces memory fragmentation at the cost of contention between threads. - Set `M_MMAP_THRESHOLD` to 2mb - This means that any allocation >= 2mb is allocated via an anonymous mmap, instead of on the heap/arena. This reduces memory fragmentation since we don't need to keep growing the heap to find big contiguous slabs of free memory. - ~~Run `malloc_trim` every 60 seconds.~~ - ~~This shaves unused memory from the top of the heap, preventing the heap from constantly growing.~~ - Removed, see: https://github.com/sigp/lighthouse/pull/2299#issuecomment-825322646 *Note: this only provides memory savings on the Linux (glibc) platform.* ## Additional Info I'm going to close #2288 in favor of this for the following reasons: - I've managed to get the memory footprint *smaller* here than with jemalloc. - This PR seems to be less of a dramatic change than bringing in the jemalloc dep. - The changes in this PR are strictly runtime changes, so we can create CLI flags which disable them completely. Since this change is wide-reaching and complex, it's nice to have an easy "escape hatch" if there are undesired consequences. ## TODO - [x] Allow configuration via CLI flags - [x] Test on Mac - [x] Test on RasPi. - [x] Determine if GNU malloc is present? - I'm not quite sure how to detect for glibc.. This issue suggests we can't really: https://github.com/rust-lang/rust/issues/33244 - [x] Make a clear argument regarding the affect of this on CPU utilization. - [x] Test with higher `M_ARENA_MAX` values. - [x] Test with longer trim intervals - [x] Add some stats about memory savings - [x] Remove `malloc_trim` calls & code		2021-05-28 05:59:45 +00:00
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tests.rs	Tune GNU malloc (#2299)	2021-05-28 05:59:45 +00:00