Date: Tue, 7 Oct 2008 09:38:04 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-threads@freebsd.org Cc: =?gb2312?q?=C7=F1=BD=A3?= <qj@huawei.com>, freebsd-net@freebsd.org, freebsd-questions@freebsd.org Subject: Re: kernel profiling: spinlock_exit consumes 36% CPU time. Message-ID: <200810070938.04673.jhb@freebsd.org> In-Reply-To: <004001c92871$fdec0a10$01000001@china.huawei.com> References: <004001c92871$fdec0a10$01000001@china.huawei.com>
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On Tuesday 07 October 2008 07:44:00 am =C7=F1=BD=A3 wrote: > Hi, folks, > =20 > I did kernel profiling when a single thread client sends UDP packets to a > single thread server on the same machine. > =20 > In the output kernel profile, the first few kernel functions that consumes > the most CPU time are listed below: > =20 > granularity: each sample hit covers 16 byte(s) for 0.01% of 25.68 seconds >=20 > % 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 tim= e=20 spent executing the handlers for any pending interrupts are attributed to=20 spinlock_exit(). =2D-=20 John Baldwin
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