Messages in this thread | | | Date | Tue, 26 Feb 2002 10:09:16 -0500 | From | Brian Ristuccia <> | Subject | Re: kernel nfsd consuming 100% CPU on 2.4.17 and 2.4.18 with reiserfs? |
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Chris Mason wrote: > > On Tuesday, February 26, 2002 08:48:02 AM -0500 Brian Ristuccia > <bristucc@sw.starentnetworks.com> wrote: > > >>It seems that kernel nfsd consumes an inordinate amount of CPU time >>during writes on this machine. With a few hundred kb/sec being written >>over NFSv3 from a 2.2.17 client, all of the nfsd threads each consume as >>much of the available CPU time as possible. On a similarly configured >>machine with ext3 instead of reiserfs, nfsd consumes much less CPU time. >> >>Is there a known issue with NFSv3 performance and reiserfs? >> > > No, it is not a known issue. Does it only happen with a 2.2.17 client, or > can you reproduce with any kernel version on the client? >
I can get it to happen with 2.2.19 and 2.4.4-pre3 as well.
So I'm pretty sure the NFS server is doing too much work somewhere.
If it matters, it's a SMP kernel running on a dual 1ghz pIII system with 2gb of memory. The filesystem resides on a linux kernel md RAID-5 array with 6 10,000 rpm disks. It's my understanding that the a machine this large should soak out the available network or disk bandwidth long before it became CPU bound serving NFS. I also did some raw IO tests to confirm that the md block device wasn't hogging up CPU time that was getting accounted to the nfsd kernel threads. I can soak that array pretty hard without soaking the CPU.
The closest machine configuration wise that I have access to is similarly configured, only with 3 disks instead of 6 and ext3 instead of reiserfs. Both machines were running exactly the same 2.4.17 image when I started having this problem. I can't reproduce the problem there, even when I do nasty things like run bonnie++ over NFS. (This isn't to say that nfsd is free on this other machine, but I'm seeing it use on the order of 2-4% CPU per nfsd thread with 8 threads and a load average of between 1 and 2 vs. 20+% and a load average of 8 on the other machine).
Thanks.
-- Brian Ristuccia
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