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Posted to github@trafficserver.apache.org by GitBox <gi...@apache.org> on 2022/11/18 08:22:30 UTC
[GitHub] [trafficserver] masaori335 opened a new pull request, #9204: Use ts::shared_lock for ReplaceablePtr
masaori335 opened a new pull request, #9204:
URL: https://github.com/apache/trafficserver/pull/9204
I have been running my own eBPF based mutex profiling tool. Recently a mutex lock shows up with the latest mater branch that I haven't seen before.
## Report from profiler
```
mutex [unknown] ::: wait time 228741.80us ::: hold time 57441.78us ::: enter count 6754 ::: try-lock failure count 0
std::__1::mutex::lock()+0x6 [libc++.so.1.0] (7f31fb7347f6)
Cache::open_read(Continuation*, ats::CryptoHash const*, HTTPHdr*, OverridableHttpConfigParams const*, CacheFragType, char const*, int)+0x42 [traffic_server] (55dd98786a32)
CacheProcessor::open_read(Continuation*, HttpCacheKey const*, HTTPHdr*, OverridableHttpConfigParams const*, long, CacheFragType)+0x27 [traffic_server] (55dd9876b5c7)
HttpCacheSM::open_read(HttpCacheKey const*, URL*, HTTPHdr*, OverridableHttpConfigParams const*, long)+0x9d [traffic_server] (55dd985f9cad)
HttpSM::do_cache_lookup_and_read()+0x169 [traffic_server] (55dd985ec0d9)
```
It looks like the `std::__1::mutex::lock` is called from `ReplaceablePtr<CacheHostTable>::ScopedReader` introduced by https://github.com/apache/trafficserver/pull/9046.
https://github.com/apache/trafficserver/blob/e37b35d79e4760d42c258a98a369c9ba827a5935/iocore/cache/Cache.cc#L3003-L3006
It loosk like replacing `std::shared_lock` with `ts::shared_mutex` mitigates the issue. At least the profiler stoped complaining.
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[GitHub] [trafficserver] SolidWallOfCode commented on pull request #9204: Use ts::shared_lock for ReplaceablePtr
Posted by GitBox <gi...@apache.org>.
SolidWallOfCode commented on PR #9204:
URL: https://github.com/apache/trafficserver/pull/9204#issuecomment-1320584686
I wonder if it is because that workload is write heavy.
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[GitHub] [trafficserver] masaori335 closed pull request #9204: Use ts::shared_lock for ReplaceablePtr
Posted by GitBox <gi...@apache.org>.
masaori335 closed pull request #9204: Use ts::shared_lock for ReplaceablePtr
URL: https://github.com/apache/trafficserver/pull/9204
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[GitHub] [trafficserver] masaori335 commented on pull request #9204: Use ts::shared_lock for ReplaceablePtr
Posted by GitBox <gi...@apache.org>.
masaori335 commented on PR #9204:
URL: https://github.com/apache/trafficserver/pull/9204#issuecomment-1320610685
Sorry, it looks like I tested with my messed working branch and misunderstood. If I look carefully, the call stack of the report doesn't match with the `Cache::key_to_vol`.
#9040 seems fine.
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