Messages in this thread |  | | Date | Fri, 20 Aug 2004 20:56:33 +0200 | From | Ingo Molnar <> | Subject | Re: [patch] voluntary-preempt-2.6.8.1-P5 |
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* K.R. Foley <kr@cybsft.com> wrote:
> Here is a latency trace generated by the NFS compile in the > stress-kernel. It is ~1.7 ms which doesn't really surprise me for the > NFS compile. I am going to take the NFS compile out of the test now > and see what else falls out.
NFS uses lock_kernel() for most of its locking. This means that the sharing and locking rules and assumptions are not clear (it's all within this opaque lock). I tried to figure out whether it would be safe to do a lock-break in nfs_cached_lookup() but it's quite hard ... Please bug the NFS-client maintainer(s) about this. To break this latency we'd have to do a lock-break in fs/nfs/dir.c:nfs_cached_lookup()'s main loop:
for(;(page = find_get_page(dir->i_mapping, desc.page_index)); desc.page_index++) {
res = -EIO;
you could try this at the end of the loop:
if (res == 0) goto out_found; if (res != -EAGAIN) break; + cond_resched(); }
but i cannot guarantee that this is correct ... It might seem to work now but break later under load, etc. It's the NFS maintainer's call.
> If it would be useful for me to provide additional information with > this, please let me know.
reports like this are perfect for most latencies. I tried to include everything that is needed normally in /proc/latency_trace itself.
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