Date: Fri, 20 Jan 2012 08:46:09 +0800 From: David Xu <listlog2011@gmail.com> To: Bruce Evans <brde@optusnet.com.au> Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org, davidxu@FreeBSD.org, John Baldwin <jhb@FreeBSD.org> Subject: Re: svn commit: r230201 - head/lib/libc/gen Message-ID: <4F18B951.6080404@gmail.com> In-Reply-To: <20120120030456.O1411@besplex.bde.org> References: <201201160615.q0G6FE9r019542@svn.freebsd.org> <4F178CDC.3030807@gmail.com> <4F17B0DE.3060008@gmail.com> <201201191023.28426.jhb@freebsd.org> <20120120030456.O1411@besplex.bde.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On 2012/1/20 0:55, Bruce Evans wrote: > On Thu, 19 Jan 2012, John Baldwin wrote: > >> On Thursday, January 19, 2012 12:57:50 am David Xu wrote: >>> rdtsc() may not work on SMP, so I have updated it to use clock_gettime >>> to get total time. >>> http://people.freebsd.org/~davidxu/bench/semaphore2/ >>> <http://people.freebsd.org/%7Edavidxu/bench/semaphore2/>; >>> >>> Still, lfence is a lot faster than atomic lock. > > I hope it does non-microbenchmarks. IIRC, jhb found that it was > actually slower in some cases. I only did micro-benchmarks on Athlon64. It depends on hardware, if it is a large machine with lots of cpu, a small conflict on dual-core machine can become a large conflict on large machine because it is possible more cpus are now running same code which becomes a bottleneck. On a large machine which has 1024 cores, many code need to be redesigned.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4F18B951.6080404>