search for: nuber_of_threads

Displaying 4 results from an estimated 4 matches for "nuber_of_threads".

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2014 Apr 17
2
[LLVMdev] multithreaded performance disaster with -fprofile-instr-generate (contention on profile counters)
...extra shards. > } Is it possible to hook on something more clever than function entry? Choosing to do this based on thread creation or something like that could make this extra check very cheap. > MAX is a fixed cap so even on systems with 100s of cores we don't do something > silly. NUBER_OF_THREADS, if supported on the OS, can limit the shards when we > only have a small number of threads in the program. NUMBER_OF_CORES, if > supported on the OS, can limit the shards. If we don't have the number of > threads, we just use the number of cores. If we don't have the number of &gt...
2014 Apr 17
9
[LLVMdev] multithreaded performance disaster with -fprofile-instr-generate (contention on profile counters)
Hi, The current design of -fprofile-instr-generate has the same fundamental flaw as the old gcc's gcov instrumentation: it has contention on counters. A trivial synthetic test case was described here: http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-October/066116.html For the problem to appear we need to have a hot function that is simultaneously executed by multiple threads -- then we will
2014 Apr 17
2
[LLVMdev] multithreaded performance disaster with -fprofile-instr-generate (contention on profile counters)
...MBER_OF_THREADS, > NUMBER_OF_CORES)); > // if shard_count changed with this, we can also call a library routine > here that does the work of allocating the actual extra shards. > } > > MAX is a fixed cap so even on systems with 100s of cores we don't do > something silly. NUBER_OF_THREADS, if supported on the OS, can limit the > shards when we only have a small number of threads in the program. > NUMBER_OF_CORES, if supported on the OS, can limit the shards. If we don't > have the number of threads, we just use the number of cores. If we don't > have the number o...
2014 Apr 18
4
[LLVMdev] multithreaded performance disaster with -fprofile-instr-generate (contention on profile counters)
...eck very cheap. > > Yea, *if* you can do it on thread creation, that would be awesome. But we don't really have a good way to model that right now. on the flip side. > > > > MAX is a fixed cap so even on systems with 100s of cores we don't do something > > silly. NUBER_OF_THREADS, if supported on the OS, can limit the shards when we > > only have a small number of threads in the program. NUMBER_OF_CORES, if > > supported on the OS, can limit the shards. If we don't have the number of > > threads, we just use the number of cores. If we don't have th...