Adding StringPiece read/write support to pickle.
This is a re-do of https://codereview.chromium.org/927183002/ which
was reverted in CL https://codereview.chromium.org/981853002/ because
of (unsubstantiated) concerns that it caused a crash.
Adding StringPiece/StringPiece16 read/write support to pickle, and
update unit tests.
The IPC perf tests do a lot of allocations which can, with large block
sizes, harm their performance. The high allocation counts also make
their performance very dependent on the quirks of the Windows heap, as
it applies undocumented heuristics to decide when to decommit memory
and when to save it for later.
And, doing unnecessary allocations is generally always a bad thing.
So, this change adds StringPiece support to PickleIterator (reading)
and Pickle (writing). The StringPiece function now handles all strings
when writing, but must be requested explicitly when reading.
ipc_mojo_perftests does more allocations than ipc_perftests. This
removes one message-sized allocation from both tests.
The unit tests were updated so that WriteString and WriteString16 are
exercised with both string objects and char/char16 arrays (no
allocations required!). Reading into StringPiece and StringPiece16 is
also tested and the tests were verified with:
out\Release\base_unittests --gtest_filter=PickleTest.*
The main performance test command line used was:
out\Release\ipc_mojo_perftests --gtest_filter=MojoChannelPerfTest.ChannelPingPong
Typical test results on HP Z620 (Windows 8.1) with thread affinity and
high-performance power settings prior to this change:
IPC_Channel_Perf_50000x_12 1140.01 ms
IPC_Channel_Perf_50000x_144 1182.55 ms
IPC_Channel_Perf_50000x_1728 1266.42 ms
IPC_Channel_Perf_12000x_20736 1289.19 ms
IPC_Channel_Perf_1000x_248832 584.619 ms
Typical test results with same settings but using base::StringPiece:
IPC_Channel_Perf_50000x_12 1123.33 ms
IPC_Channel_Perf_50000x_144 1164.53 ms
IPC_Channel_Perf_50000x_1728 1242.99 ms
IPC_Channel_Perf_12000x_20736 1186.84 ms
IPC_Channel_Perf_1000x_248832 496.469 ms
Modest improvement with small buffers, but significant speedup with large buffers.
Typical test results with large-blocks only prior to this change:
IPC_Channel_Perf_1000x_248832 1211.33 ms
IPC_Channel_Perf_1000x_248832 961.404 ms
IPC_Channel_Perf_1000x_248832 600.911 ms
IPC_Channel_Perf_1000x_248832 468.356 ms
IPC_Channel_Perf_1000x_248832 430.859 ms
IPC_Channel_Perf_1000x_248832 425.147 ms
Typical test results with large-blocks only (base::StringPiece):
IPC_Channel_Perf_1000x_248832 909.571 ms
IPC_Channel_Perf_1000x_248832 731.435 ms
IPC_Channel_Perf_1000x_248832 493.697 ms
IPC_Channel_Perf_1000x_248832 417.966 ms
IPC_Channel_Perf_1000x_248832 397.377 ms
IPC_Channel_Perf_1000x_248832 397.725 ms
Note that it takes a while for the Windows heap to 'realize' that it
should hang on to some of the large blocks which is why performance
increases over multiple runs.
Chrome will not immediately be affected because StringPiece reading has
to be explicitly selected. Note that the effect on ipc_perftests is
more variable due to the odd Windows heap heuristics.
Reliable results require setting the power plan to high-performance.
On Linux this is done with this command:
sudo cpupower frequency-set --governor performance
The ipc_perftests command-line is:
out/Release/ipc_perftests --gtest_filter=IPCChannelPerfTest.ChannelPingPong
Typical before/after Linux results for ipc_perftests are:
IPC_Channel_Perf_50000x_12 465.271 ms
IPC_Channel_Perf_50000x_144 480.224 ms
IPC_Channel_Perf_50000x_1728 510.871 ms
IPC_Channel_Perf_12000x_20736 318.016 ms
IPC_Channel_Perf_1000x_248832 309.325 ms
IPC_Channel_Perf_50000x_12 459.245 ms
IPC_Channel_Perf_50000x_144 479.347 ms
IPC_Channel_Perf_50000x_1728 506.57 ms
IPC_Channel_Perf_12000x_20736 289.583 ms
IPC_Channel_Perf_1000x_248832 255.083 ms
Before after Linux results for ipc_mojo_perftests:
IPC_Channel_Perf_50000x_12 670.727 ms
IPC_Channel_Perf_50000x_144 713.6 ms
IPC_Channel_Perf_50000x_1728 808.157 ms
IPC_Channel_Perf_12000x_20736 464.221 ms
IPC_Channel_Perf_1000x_248832 365.258 ms
IPC_Channel_Perf_50000x_12 653.12 ms
IPC_Channel_Perf_50000x_144 697.418 ms
IPC_Channel_Perf_50000x_1728 772.575 ms
IPC_Channel_Perf_12000x_20736 446.315 ms
IPC_Channel_Perf_1000x_248832 348.38 ms
So, consistent improvements on Linux.
Review URL: https://codereview.chromium.org/987033003
Cr-Commit-Position: refs/heads/master@{#319810}
CrOS-Libchrome-Original-Commit: eaa3896066e3b3c5e742a2dea4f87fe5e8e5dda4
4 files changed