commit cd51f067a7d5d33d695016bd1dc8a139bf736338
author chiniforooshan <chiniforooshan@chromium.org> Fri Apr 21 20:13:31 2017
committer Commit bot <commit-bot@chromium.org> Fri Apr 21 20:13:31 2017
tree 760bbac17e3125f9fedb95bd28e1c51f679d5529
parent cf5379cbc7095de979bba11519acc126a99532d2

tracing: Stream processing for some importers

This implements stream processing for trace event importer, gzip
importer, and Linux trace event importer.

A tr.useTraceStreams flag is introduced and is disabled by default,
for now, until all importers support stream processing and the
performance is reasonable.

I tested that if I set tr.useTraceStream to true, I can successfully
run trace_processor/bin/process_traces on a ~700M trace file. However,
it is slow. The source of slowness is oboe.js itself. After a little
bit investigation, I think there are some optimizations that can be
done in oboe.js, which I will send in future CLs.

Note that this is still with the assumption that traces fit in memory. If we
want to get rid of this assumption in the future:
- d8 should support reading chunks of data from a file.
- tr.b.TraceStream read methods should return promises.
- oboe.js should support returning just the start and end position of a value
  instead of the value itself, for values that do not fit in memory.

BUG=catapult:#2826

Review-Url: https://codereview.chromium.org/2755943002