Date: Tue, 16 Oct 2001 09:48:45 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Dag-Erling Smorgrav <des@ofug.org> Cc: Bruce Evans <bde@zeta.org.au>, <cvs-committers@FreeBSD.ORG>, <cvs-all@FreeBSD.ORG> Subject: Re: cvs commit: src/sys/vm vnode_pager.c Message-ID: <200110161648.f9GGmjm31651@apollo.backplane.com> References: <200110161629.f9GGTju31481@apollo.backplane.com> <xzpr8s3wnee.fsf@flood.ping.uio.no>
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:Matthew Dillon <dillon@apollo.backplane.com> writes:
:> ffs_sync() in -current is doing a lot of mutex operations
:> in the loop. If you have various -current mutex debugging
:> options turned on, even the default ones I think, this could
:> be responsible for the latency you are experiencing. Each
:> scan loop is doing four mutex ops.
:
:So, what changed in the witness code to make it so slow (or in the FFS
:code to make it perform so many mutex operations) around late June /
:early July?
:
:DES
:--
:Dag-Erling Smorgrav - des@ofug.org
You'll have to inquire. I don't know. Even a small change
could have a large effect considering that each sync is doing
several hundred thousand mutex calls. If you think about it,
a mutex call taking a mere 1uS could result in very
noticeable delays.
-Matt
Matthew Dillon
<dillon@backplane.com>
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