Buffer LLVM's object output stream #53524
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In some profiling on OSX I saw the `write` syscall as quite high up on the profiling graph, which is definitely not good! It looks like we're setting the output stream of an object file as directly to a file descriptor which means that we run the risk of doing lots of little writes rather than a few large writes. This commit fixes this issue by adding a buffered stream on the output, causing the `write` syscall to disappear from the profiles on OSX.
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r? @aturon (rust_highfive has picked a reviewer for you, use r? to override) |
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r? @eddyb |
| @@ -556,7 +556,8 @@ LLVMRustWriteOutputFile(LLVMTargetMachineRef Target, LLVMPassManagerRef PMR, | |||
| } | |||
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| #if LLVM_VERSION_GE(7, 0) | |||
| unwrap(Target)->addPassesToEmitFile(*PM, OS, nullptr, FileType, false); | |||
| buffer_ostream BOS(OS); | |||
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Is there a reason this is only done on 7.0+? Seems like we could do it for other LLVMs as well.
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I didn't want to muck around with older versions without testing, so I opted to leave it here (it doesn't really matter for older llvm, a slightly slower compiler is the least of those worries)
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Aug 20, 2018
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@bors r+ |
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📌 Commit 9d54bf8 has been approved by |
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Buffer LLVM's object output stream In some profiling on OSX I saw the `write` syscall as quite high up on the profiling graph, which is definitely not good! It looks like we're setting the output stream of an object file as directly to a file descriptor which means that we run the risk of doing lots of little writes rather than a few large writes. This commit fixes this issue by adding a buffered stream on the output, causing the `write` syscall to disappear from the profiles on OSX.
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☀️ Test successful - status-appveyor, status-travis |
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In some profiling on OSX I saw the
writesyscall as quite high up onthe profiling graph, which is definitely not good! It looks like we're
setting the output stream of an object file as directly to a file
descriptor which means that we run the risk of doing lots of little
writes rather than a few large writes.
This commit fixes this issue by adding a buffered stream on the output,
causing the
writesyscall to disappear from the profiles on OSX.