THRIFT-5709: Drastically improve to_string() performance. #2806
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Creating locales is surprisingly expensive. We have an application where we - especially during tests - write large amounts of Thrift dumps to disk, and is this application we currently spend around 17% of total CPU time in std::locale's constructor. With this change, it's basically down to zero.
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Why do we need 4 instances? |
I don't think we do, I just wanted to make the change as small as possible. Would you prefer a global constant (in an anonymous namspace probably)? |
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Well, I just thought if we are going to optimize, why don't we do it right ... so yes, would make sense to me, if that's not causing other overhead, too much confusion or work, then I'm for it. |
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@Jens-G I have updated the PR to use a single, TU-local locale. |
tinloaf
commented
May 30, 2023
| @@ -32,10 +32,15 @@ | |||
| namespace apache { | |||
| namespace thrift { | |||
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| // unnamed namespace to enforce internal linkage - could be done with 'inline' when once have C++17 | |||
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TODO: when/once is duplicate here.
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Currently, the
to_string()overloads inTToString.hcall thestd::localeconstructor for every single call. Creating locales is surprisingly expensive. We have an application where we - especially during tests - write large amounts of Thrift dumps to disk, and is this application we currently spend around 17% of total CPU time in std::locale's constructor (building with MSVC, in a Release build - other compilers might optimize this away?). With this change, it's basically down to zero.Since we always create the exact same locale anyways, using a
const staticone does not hurt.[skip ci]anywhere in the commit message to free up build resources.