Jun Wu d8e775f423 tracing-collector: limit maximum count of spans ... Summary: Some functions might be called very frequently. For example, `phases.phasecache.loadphaserevs` might be called 100k+ times. That makes the tracing data harder to process. Limit the count of spans to 1k by default so the data is cheaper to process, and some highly repetitive cases can now be reasoned about. Note the limit is only put on static Span Ids. If a span uses dynamic metadata or ask for different Span Ids each time, they will not be limited. In debugshell, td = %trace repo.revs('smartlog()') len(td.serialize()) dropped from 6MB to 0.87MB. It's also possible to reason about: td = %trace len(repo.revs('ancestors(.)')) in debugshell (taking 30s, 98KB serialized, vs 21s without tracing), while previously the result would be too large to show (`%trace` just hangs). Reviewed By: DurhamG Differential Revision: D23307793 fbshipit-source-id: 3c1e9885ce7a275c2abd8935a4e4539a4f14ce83		2020-08-27 18:14:29 -07:00
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src	tracing-collector: limit maximum count of spans	2020-08-27 18:14:29 -07:00
Cargo.toml	tracing: make it write to the log eco-system	2020-03-10 14:16:37 -07:00