Date: Wed, 08 Oct 2008 15:51:48 +0800 From: =?gb2312?B?x/G9ow==?= <qj@huawei.com> To: 'John Baldwin' <jhb@freebsd.org>, freebsd-threads@freebsd.org Cc: freebsd-net@freebsd.org, freebsd-questions@freebsd.org Subject: RE: kernel profiling: spinlock_exit consumes 36% CPU time. Message-ID: <000a01c9291a$b81fa560$01000001@china.huawei.com> In-Reply-To: <200810070938.04673.jhb@freebsd.org>
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Many thanks for the information. Could we say that interrupt handlers consumed ~36% execution time? Is this number too high? Is it possible that we abuse the use of critical sections in kernel? Looking forward to your options. Many thanks. Qiu Jian On Tuesday 07 October 2008 07:44:00 am Ηρ½£ wrote: > Hi, folks, > > I did kernel profiling when a single thread client sends UDP packets > to a single thread server on the same machine. > > In the output kernel profile, the first few kernel functions that > consumes the most CPU time are listed below: > > granularity: each sample hit covers 16 byte(s) for 0.01% of 25.68 > seconds > > % cumulative self self total > time seconds seconds calls ms/call ms/call name > 42.4 10.88 10.88 0 100.00% __mcount [1] > 36.1 20.14 9.26 17937541 0.00 0.00 spinlock_exit [4] > 4.2 21.22 1.08 3145728 0.00 0.00 in_cksum_skip [40] > 1.8 21.68 0.45 7351987 0.00 0.00 generic_copyin [43] > 1.1 21.96 0.29 3146028 0.00 0.00 generic_copyout [48] > 1.0 22.21 0.24 2108904 0.00 0.00 Xint0x80_syscall [3] > 0.8 22.42 0.21 6292131 0.00 0.00 uma_zalloc_arg [46] > 0.8 22.62 0.20 1048576 0.00 0.00 soreceive_generic [9] > > It is very strange that spinlock_exit consumes over 36% CPU time while > it seems a very simple function. It's because the intr_restore() re-enables interrupts and the resulting time spent executing the handlers for any pending interrupts are attributed to spinlock_exit(). -- John Baldwin
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