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Date: Thu, 23 Oct 2008 14:36:28 +0200 From: Max Kellermann <max@...mpel.org> To: linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org, trond.myklebust@....uio.no Cc: harry@...os.washington.edu Subject: Re: High load in 2.6.27, NFS / rpcauth_lookup_credcache()? On 2008/10/22 11:12, Max Kellermann <max@...mpel.org> wrote: > after I was able to fix http://lkml.org/lkml/2008/10/17/147, the > server which was already upgraded to 2.6.27.2 still gets very high > load. It is a web server with NFS file storage (NetApp), and while > the others in the cluster (kernel 2.6.25) have a load of 1-3, 2.6.27.2 > gets 30-50. > > I did an oprofile, with the following results (server just started, > load "only" 5-10): > > 87593 56.1116 (no location information) vmlinux > vmlinux rpcauth_lookup_credcache > 16037 10.2732 auth_generic.c:0 vmlinux > vmlinux generic_match > 6460 4.1382 (no location information) php4 > php4 (no symbols) > 2478 1.5874 (no location information) libc-2.7.so > libc-2.7.so (no symbols) > [...] > > We havn't configured any special authentication method. It is a NFSv3 > over UDP mount, but the kernel has NFSv4 and therefore KRB5 enabled. > > Any ideas why rpcauth_lookup_credcache() goes overboard with CPU > usage? I have bisected the problem: 98a8e323 is the result ("SUNRPC: Add a helper rpcauth_lookup_generic_cred()"). 5c691044 is ok. See the attached oprofile annotation data for both commits. I guess that the function rpcauth_lookup_credcache() is waiting for a spinlock too often and too long. Trond, any idea? Harry: added you to Cc because your problem sounds similar. Max View attachment "annotate.98a8e3239427051f5d44f2025b398bdcc3918f37" of type "text/plain" (7840 bytes) View attachment "annotate.5c691044ecbca04dd558fca4c754121689fe1b34" of type "text/plain" (7841 bytes)
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