commit b99901c433fcf67b5617543edef25e18d915735d
author Jens Johansen <jensj@google.com> Tue May 31 08:17:33 2022 +0000
committer Commit Bot <commit-bot@chromium.org> Tue May 31 08:17:33 2022 +0000
tree 3d02553608e9437010ef0677e1e5a679c76a76d4
parent a801368f80f85553682816c67c9e7dc3ea90337d

[CFE] Speedup dill serialization after slowdown in 548bff1

548bff1 was meant to do less.
It actually turns out slower though:

Before 548bff1:
[ 07:52 | 100.0% | + 2252 | -    0 ]: weak/variance/unconstrained_inference

real    7m58.017s
user    11m15.944s
sys     2m42.890s

=> 209.5 ms per test.

After 548bff1:
[ 08:47 | 100.0% | + 2252 | -    0 ]: weak/variance/unconstrained_inference

real    8m53.362s
user    10m27.086s
sys     1m10.925s

=> 234.0 ms per test.

What it did was, that it introduced - I'm guessing this is the reason -
some non-monomorphism in the serialization code by having sinks of
different types.

Running
`time out/ReleaseX64/dart --enable-asserts pkg/front_end/test/fasta/weak_suite.dart --traceStepTiming -DupdateExpectations=false -DsemiFuzz=false`
(with code changed so it's three shards, running only the first one)

I get numbers like this for writing the dill file though:

Before 548bff1: 0:01:28.369107
 After 548bff1: 0:01:44.803383

(again this is for 1 out of 3 shards, but illustrates the point ---
serialization is slower).

This CL changes this to always serialize into the same sink (in memory),
then - if needed (as in the original CL) - write it to disk.
This gets (again with 1 out of 3 shards) writing the dill down to
0:01:21.872812, and the total run looks like this:

[ 07:18 | 100.0% | + 2252 | -    0 ]: weak/variance/unconstrained_inference

real    7m23.361s
user    10m48.069s
sys     1m30.336s

=> 194.4 ms per test.

(rebased run:

[ 07:13 | 100.0% | + 2254 | -    0 ]: weak/variance/unconstrained_inference

real    7m18.828s
user    10m44.163s
sys     1m31.777s

=> 192.1 ms per test.)

Change-Id: I2906807bbab407fb499aa910afd20f41347bc3c6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/245374
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Jens Johansen <jensj@google.com>