From mboxrd@z Thu Jan 1 00:00:00 1970 From: xuehai zhang Subject: Re: open/stat64 syscalls run faster on Xen VM than standard Linux Date: Mon, 28 Nov 2005 09:50:43 -0600 Message-ID: <438B2753.4020401@cs.uchicago.edu> References: <907625E08839C4409CE5768403633E0B0EAAC4@sefsexmb1.amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <907625E08839C4409CE5768403633E0B0EAAC4@sefsexmb1.amd.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "Petersson, Mats" Cc: Kate Keahey , Xen Mailing List , Tim Freeman List-Id: xen-devel@lists.xenproject.org Mats, I mounted the loopback file in dom0, chrooted to the mountpoint and redid the experiment. The results is attached below. The time of open and stat64 calls is similar to the XenLinux case and also much smaller than the standard Linux case. So, either using loopback file as backend of XenLinux or directly mounting it in local filesystem will result in some benefit (maybe just caused by the extra layer of block caching) for the performance of some system calls. # strace -c /bin/sh -c /bin/echo foo % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 21.93 0.000490 490 1 write 16.34 0.000365 24 15 old_mmap 15.26 0.000341 38 9 3 open 9.62 0.000215 43 5 read 7.97 0.000178 10 18 brk 7.79 0.000174 87 2 munmap 4.07 0.000091 8 11 rt_sigaction 3.27 0.000073 12 6 close 2.91 0.000065 11 6 fstat64 2.28 0.000051 9 6 rt_sigprocmask 2.15 0.000048 24 2 access 1.75 0.000039 13 3 uname 1.66 0.000037 19 2 stat64 0.40 0.000009 9 1 getpgrp 0.40 0.000009 9 1 getuid32 0.36 0.000008 8 1 time 0.36 0.000008 8 1 getppid 0.36 0.000008 8 1 getgid32 0.31 0.000007 7 1 getpid 0.27 0.000006 6 1 execve 0.27 0.000006 6 1 geteuid32 0.27 0.000006 6 1 getegid32 ------ ----------- ----------- --------- --------- ---------------- 100.00 0.002234 95 3 total Thanks. Xuehai Petersson, Mats wrote: >>-----Original Message----- >>From: xen-devel-bounces@lists.xensource.com >>[mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of >>Anthony Liguori >>Sent: 28 November 2005 14:39 >>To: xuehai zhang >>Cc: Xen Mailing List >>Subject: Re: [Xen-devel] open/stat64 syscalls run faster on >>Xen VM than standard Linux >> >>This may just be the difference between having the extra >>level of block caching from using a loop back device. >> >>Try running the same benchmark on a domain that uses an >>actual partition. While the syscalls may appear to be >>faster, I imagine it's because the cost of pulling in a block >>has already been payed so the overall workload is unaffected. > > > And this would be the same as running standard linux with the loopback > file-system mounted and chroot to the local file-system, or would that > be different? [I'm asking because I don't actually understand enough > about how it works to know what difference it makes, and I would like to > know, because at some point I'll probably need to know this.] > > -- > Mats > >>Regards, >> >>Anthony Liguori >> >>xuehai zhang wrote: > > [snip] > >