SMP, NFS, and 2.6

I've heard from some (via google searchs) that there are issues with NFS + SMP when using the 2.6 kernel. Assuming I'm using 2.6.11.5 w/ the NFS-ALL patches applied should I be concerned about running SMP (dual cpu pentium 4 doing pretty much only NFSv3 TCP, but looking toward NFSv4)?

Assuming it's ok to use SMP on a heavy use NFS server, should I enable or disable hyperthreading? I'd assume that for NFS hyperthreading would be good, but that's only a guess.

Thanks,

Chris

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Quoted 12 lines · Chris Penney

I've heard from some (via google searchs) that there are issues with NFS + SMP when using the 2.6 kernel. Assuming I'm using 2.6.11.5 w/ the NFS-ALL patches applied should I be concerned about running SMP (dual cpu pentium 4 doing pretty much only NFSv3 TCP, but looking toward NFSv4)?

Assuming it's ok to use SMP on a heavy use NFS server, should I enable or disable hyperthreading? I'd assume that for NFS hyperthreading would be good, but that's only a guess.

Thanks,

Quoted 2 lines

Chris

Are you referring to the dcache problems with XFS? I think it was only a problem when the NFS server was exporting an XFS file system. I also haven't checked in some time, but I believe those problems have since been fixed.

Neil

Quoted 15 lines · Neil Horman

Quoted 14 lines · Chris Penney

I've heard from some (via google searchs) that there are issues with NFS + SMP when using the 2.6 kernel. Assuming I'm using 2.6.11.5 w/ the NFS-ALL patches applied should I be concerned about running SMP (dual cpu pentium 4 doing pretty much only NFSv3 TCP, but looking toward NFSv4)?

Assuming it's ok to use SMP on a heavy use NFS server, should I enable or disable hyperthreading? I'd assume that for NFS hyperthreading would be good, but that's only a guess.

Thanks,

Chris

Quoted 5 lines

Are you referring to the dcache problems with XFS? I think it was only a problem when the NFS server was exporting an XFS file system. I also haven't checked in some time, but I believe those problems have since been fixed.

Neil

Yes, most of what I read was regarding XFS. I was not sure if there were any issues outside of that (I'm using JFS right now).

As far as HyperThreading my testing so far has shown that under heavy loads enabling HyperThreading on a dual-cpu P4 box seems to be a good thing. I would grab 30s of packets with ethereal and look at the NFS stats and the responce time on writes/commits (which we see a fair bit of) were at least 33% faster if not more. I'm not sure if that's an accurate way to measure though -- I know enough to be dangerous, but I'm not an expert.

Chris

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Quoted 1 line · Chris Penney

On Tue, 29 Mar 2005 16:13:24 -0500, Neil Horman <[email protected]>

Quoted 20 lines

Quoted 20 lines · Chris Penney

Quoted 6 lines

I've heard from some (via google searchs) that there are issues with NFS + SMP when using the 2.6 kernel. Assuming I'm using 2.6.11.5 w/ the NFS-ALL patches applied should I be concerned about running SMP (dual cpu pentium 4 doing pretty much only NFSv3 TCP, but looking toward NFSv4)?

Quoted 7 lines

Assuming it's ok to use SMP on a heavy use NFS server, should I enable or disable hyperthreading? I'd assume that for NFS hyperthreading would be good, but that's only a guess.

Thanks,

Chris

Are you referring to the dcache problems with XFS? I think it was only a problem when the NFS server was exporting an XFS file system. I also haven't checked in some time, but I believe those problems have since been fixed.

Quoted 4 lines

Quoted 1 line

Neil

Yes, most of what I read was regarding XFS. I was not sure if there were any issues outside of that (I'm using JFS right now).

None that I'm aware of, but my knoweldge is far from exhaustive :)

Quoted 7 lines

As far as HyperThreading my testing so far has shown that under heavy loads enabling HyperThreading on a dual-cpu P4 box seems to be a good thing. I would grab 30s of packets with ethereal and look at the NFS stats and the responce time on writes/commits (which we see a fair bit of) were at least 33% faster if not more. I'm not sure if that's an accurate way to measure though -- I know enough to be dangerous, but I'm not an expert.

Neither am I :). You testing seems reasonable to me (at least for what you are trying to measure currently). IIRC the Linux scheduler is built to take advantage of the shared resources available on hyperthreaded processors and schedules accordingly. In general I think its a good idea to turn on. I believe there are some pessimal workloads that can cause worse performance with HT on, than with HT off, but I believe you really have to work hard to produce those.

Regards
Neil

Quoted 11 lines

Chris

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