Optimize the size of our JSON

Catapult (Chrome tracing) has a hard upper limit of 256 MB of JSON data.
This is independent of the number of events, because V8 can't store a
single string longer than that. Before these changes, longer traces
(eg all GL GMs, which was my test case) would be much larger (306 MB).

This CL includes four changes that help to reduce the text size:

1) Offset timestamps (saved 7.3 MB)
2) Limit timestamps and durations to 3 digits (saved 10.7 MB)
3) Shorten thread IDs (saved 7.2 MB)
4) Omit categories from JSON (saved 25.7 MB)

Note that category filtering still works, this just prevents us from
writing the categories to the JSON, which was of limited value.

At this point, my 306 MB file is now 255.3 MB, and loads.

Bug: skia:
Change-Id: Iaafc84025ddd52904f1ce9c1c2e9cbca65113079
Reviewed-on: https://skia-review.googlesource.com/35523
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/trace/SkChromeTracingTracer.h b/tools/trace/SkChromeTracingTracer.h
index 34fbbae393..a9e0966419 100644
--- a/tools/trace/SkChromeTracingTracer.h
+++ b/tools/trace/SkChromeTracingTracer.h
@@ -50,7 +50,7 @@ private:
     void flush();
 
     enum {
-        // Events are variable size, but most commonly 56 bytes, assuming 64-bit pointers and
+        // Events are variable size, but most commonly 48 bytes, assuming 64-bit pointers and
         // reasonable packing. This is a first guess at a number that balances memory usage vs.
         // time overhead of allocating blocks.
         kBlockSize = 512 * 1024,