This improves performance with sandboxing.
One can have Bazel output performance data [1][2], which can be
viewed via chrome://tracing or https://ui.perfetto.dev/.
With Perfetto, the following SQL queries [3][4] can summarize
the sandboxing metrics, as well as the actual compilation
time. http://screen/5TxbeZTso4gNDfD
Note that the dur column is in nanoseconds, so we convert
to seconds. These numbers could further be divided by
the number of processes (in my case 48) to get a scaled output.
SELECT SUM(dur) / 1000000000.0 FROM slice WHERE name = "sandbox.createFileSystem";
SELECT SUM(dur) / 1000000000.0 FROM slice WHERE name = "sandbox.delete";
SELECT SUM(dur) / 1000000000.0 FROM slice WHERE name = "subprocess.run";
I benchmarked the local compilation of //:skia_public using
--config=clang_linux (our custom Linux toolchain). I was
sure to clear the Bazel cache before each run and not count
the time to download/update a toolchain for the first time.
The control measurements (without this CL) are:
Wall Time = 272.2s
sandbox.createFileSystem = 5466.9s
subprocess.run = 2961.0s
sandbox.delete = 4112.3s
With this CL:
Wall Time = 53.9s (5.05x faster)
sandbox.createFileSystem = 403.4s
subprocess.run = 1610.3s
sandbox.delete = 348.8s
The control measurement is a touch misleading. Due to it being
so slow, I had recommended developers use a ramdisk when building
on machines with sufficient RAM via the Bazel flag
--sandbox_base=/dev/shm
Here is the control measurement when using a RAM disk:
Wall Time = 21.2s
sandbox.createFileSystem = 58.9s
subprocess.run = 705.1s
sandbox.delete = 46.6s
With this CL and a RAM disk:
Wall Time = 19.2s (10% faster)
sandbox.createFileSystem = 21.8s
subprocess.run = 722.9s
sandbox.delete = 16.2s
For devs who cannot or are not using a RAM disk, this is
a huge win. With a RAM disk, it's a modest improvement.
On an RBE build, this had minimal impact. I did my best
to bust the action cache with a fake define and the before
and after times were about the same.
This was inspired by [5] and [6].
[1] Add --profile=/tmp/profile.gz to any command
[2] https://bazel.build/rules/performance#performance-profiling
[3] https://perfetto.dev/docs/quickstart/trace-analysis#sample-queries
[4] https://perfetto.dev/docs/analysis/sql-tables#slice
[5] 93f21c9ef3
[6] 311acff345
Change-Id: Iceb2606e86111159141a286d01fc002d09fe3fe4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/547822
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
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