tree 25c98fd7667238936fe9572e4fc387382e4e2a4e
parent d559295a709d6878205b6d09e797368747d7aa4b
author Marc-Antoine Ruel <maruel@google.com> 1685046590 +0000
committer CQ Bot <fuchsia-internal-scoped@luci-project-accounts.iam.gserviceaccount.com> 1685046590 +0000

[engine] Reuse stdout buffer for git operations and exec

Since parallel checks are always limited to NumCPU()+2, this limits the
number of stdout buffers created.

This reduce memory usage and fragmentation for exec(). Create three
16kib buffers to reduce initial fragmentation.

This enables running git commands in parallel. For now, only git diff
runs in parallel.

Improvements all around for memory allocation, with significant delta:

name                   old alloc/op   new alloc/op   delta
CtxOsExec                 137kB ± 0%      70kB ± 0%  -49.01%  (p=0.004 n=5+6)
CtxOsExec100             9.07MB ± 0%    2.55MB ± 5%  -71.85%  (p=0.004 n=5+6

Change-Id: If9c92826db94d0bb2193827dfa8fb7d3f7830060
Reviewed-on: https://fuchsia-review.googlesource.com/c/shac-project/shac/+/859576
Reviewed-by: Oliver Newman <olivernewman@google.com>
Commit-Queue: Marc-Antoine Ruel <maruel@google.com>