What settings had you been using and what had been measured, when you got 2% slowdown? In our test (latency related) I got following results: normal jemalloc: %99 <= 87 usec (Avg: 65 usec) inactive profiling: %99 <= 88 usec (Avg: 66 usec)
MALLOC_CONF="prof:true,prof_active:true,lg_prof_sample:19,prof_accum:true,prof_prefix:jeprof.out" prof-libgcc: %99 <= 125 usec (Avg: 70 usec) prof-libunwind: %99 <= 146 usec (Avg: 76 usec) So in average slowdown is 6% for libgcc and 15% for libunwind. But for distribution (99% < X) slowdown is 42% or 65% depending on library, which is huge difference. For 64 Kb numbers are dramatic: 154% (99% < X) performance lose. Do I miss something in configuration? On Tue, Jan 14, 2014 at 10:22 PM, Jason Evans <[email protected]> wrote: > On Dec 22, 2013, at 11:41 PM, Evgeniy Ivanov <[email protected]> wrote: >> I need to profile my application running in production. Is it >> performance safe to build jemalloc with "--enable-prof", start >> application with profiling disabled and enable it for short time >> (probably via mallctl() call), when I need? I'm mostly interested in >> stacks, i.e. opt.prof_accum. Or are there better alternatives in >> Linux? I've tried perf, but it just counts stacks and doesn't care >> about amount of memory allocated. There is also stap, but I haven't >> try it yet. > > Yes, you can use jemalloc's heap profiling as you describe, with essentially > no performance impact while heap profiling is inactive. You may even be able > to leave heap profiling active all the time with little performance impact, > depending on how heavily your application uses malloc. At Facebook we leave > heap profiling active all the time for a wide variety of server applications; > there are only a couple of exceptions I'm aware of for which the performance > impact is unacceptable (heavy malloc use, ~2% slowdown when heap profiling is > active). > > Jason -- Cheers, Evgeniy _______________________________________________ jemalloc-discuss mailing list [email protected] http://www.canonware.com/mailman/listinfo/jemalloc-discuss
