Date: Thu, 31 Dec 2009 17:22:26 -0500 From: jhell <jhell@DataIX.net> To: =?ISO-8859-15?Q?Micka=EBl_Maillot?= <mickael.maillot@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS prefetch problem Message-ID: <alpine.BSF.2.00.0912311708440.72873@qvzrafvba.5c.ybpny> In-Reply-To: <ea7b7b810912310813x61af52acs5ecabd5615ce83d8@mail.gmail.com> References: <ea7b7b810912310813x61af52acs5ecabd5615ce83d8@mail.gmail.com>
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[-- Attachment #1 --] -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Thu, 31 Dec 2009 11:13, mickael.maillot@ wrote: > this bug is referenced: > http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6859997 > and a good description can be found here: > http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6861397 > and a long thread on zfs-discuss > http://mail.opensolaris.org/pipermail/zfs-discuss/2009-July/029710.html > > i use bob friesenhahn's script to test (with little mod) > http://www.simplesystems.org/users/bfriesen/zfs-discuss/zfs-cache-test.ksh > > so i test on my hardware for reading 3000 8M files > > without prefetch: no problem > initial > real 7m49.039s > user 0m2.931s > sys 0m22.574s > second > real 7m48.080s > user 0m2.858s > sys 0m32.559s > > with prefetch enable: > initial > real 2m55.163s > user 0m2.244s > sys 0m10.072s > second > real 7m37.522s > user 0m2.367s > sys 0m10.565s > > ok i hit the same bug. > it was fix by this commit: > http://hg.intevation.org/mirrors/opensolaris.org/onnv-gate/rev/0e96dd3b905a > which add kstats for prefetch and a bug in rollback (not for us) > > the only modif for the prefetch + arc problem is resolv by: > --- dmu_zfetch.c.orig 2009-12-31 15:46:15.211700719 +0100 > +++ dmu_zfetch.c 2009-12-31 15:46:42.915461251 +0100 > @@ -323,7 +323,8 @@ > * we will read "len" blocks before "striding". > */ > if (zh->zst_offset >= zs->zst_offset && > - zh->zst_offset < zs->zst_offset + zs->zst_len) { > + zh->zst_offset < zs->zst_offset + zs->zst_len && > + prefetched) { > /* already fetched */ > rc = 1; > goto out; > > with this patch i have: > initial > real 2m57.614s > user 0m2.228s > sys 0m10.054s > second > real 2m45.403s > user 0m2.445s > sys 0m9.726s > third > real 2m16.381s > user 0m2.152s > sys 0m9.136s > > looks good. > tested on 8-STABLE amd64, with/without log/cache ssd. (but not with zil_disable) > Thanks for the heads up on this. I have applied the following to a stable/7 system @r201336 "The obrien new year copyright ;)" and will write back with further results. Attached is a patch to r201336. Happy New Years! - -- Thu Dec 31 17:08:44 2009 jhell -----BEGIN PGP SIGNATURE----- iQEcBAEBAgAGBQJLPSQtAAoJEJBXh4mJ2FR+SdcH/jb7j6Fb7OfvRwY2yNpoJ3iG li5NZ3Ukj7CC4XNIYS3nal3xg55oIvzTfjX6+c7MCCpbx2p3RuAvMh2wOcU+B2vn Pdvd0sDFRG96caUrdJ0O1ZIs2SmdVSKz/vxQEVtWW6EUq/4NOd+D243zDJxqOYED CkgobJmymWQ9swxR0uvH0vlsj8mK481GkMJPWVKDthGvjLU72dp+A1sCEj1e7B3J b9n48m66jUSYJwxO0Kyf8oHNVYdUvOURcwrSnS0yUdZlsUIn0ALHEGkO26N3Jl0V Te9CFuNaQfpsswTMiZQvpMVfhPk+292tGXsERaxx4m46SyWFnZYpXu8qUIwqhpM= =0pfh -----END PGP SIGNATURE----- [-- Attachment #2 --] --- dmu_zfetch.c.orig 2009-12-31 16:54:17.921496283 -0500 +++ dmu_zfetch.c 2009-12-31 16:58:16.278113395 -0500 @@ -324,7 +324,8 @@ * we will read "len" blocks before "striding". */ if (zh->zst_offset >= zs->zst_offset && - zh->zst_offset < zs->zst_offset + zs->zst_len) { + zh->zst_offset < zs->zst_offset + zs->zst_len && + prefetched) { /* already fetched */ rc = 1; goto out;
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