Date: Sat, 3 Sep 2005 00:21:56 +0000 (UTC) From: Don Lewis <truckman@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/kern vfs_subr.c Message-ID: <200509030021.j830LuEJ099393@repoman.freebsd.org>
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truckman 2005-09-03 00:21:56 UTC
FreeBSD src repository
Modified files: (Branch: RELENG_6)
sys/kern vfs_subr.c
Log:
MFC vfs_subr.c 1.636 and 1.642
vfs_subr.c 1.642 fixes a small race condition in vlrureclaim() and depends
on 1.636.
Modified files:
sys/kern vfs_subr.c
Log:
- Allow vnlru to drop giant if the filesystem does not require it. The
vnlru proc is extremely inefficient, potentially iteration over tens of
thousands of vnodes without blocking. Droping Giant allows other threads
to preempt us although we should revisit the algorithm to fix the runtime
problems especially since this may hold up all vnode allocations.
- Remove the LK_NOWAIT from the VOP_LOCK in vlrureclaim. This provides
a natural blocking point to help alleviate the situation described above
although it may not technically be desirable.
- yield after we make a pass on all mount points to prevent us from
blocking other threads which require Giant.
MFC after: 2 weeks
Revision Changes Path
1.636 +11 -2 src/sys/kern/vfs_subr.c
Modified files:
sys/kern vfs_subr.c
Log:
Back out the removal of LK_NOWAIT from the VOP_LOCK() call in
vlrureclaim() in vfs_subr.c 1.636 because waiting for the vnode
lock aggravates an existing race condition. It is also undesirable
according to the commit log for 1.631.
Fix the tiny race condition that remains by rechecking the vnode
state after grabbing the vnode lock and grabbing the vnode interlock.
Fix the problem of other threads being starved (which 1.636 attempted
to fix by removing LK_NOWAIT) by calling uio_yield() periodically
in vlrureclaim(). This should be more deterministic than hoping
that VOP_LOCK() without LK_NOWAIT will block, which may not happen
in this loop.
Reviewed by: kan
MFC after: 5 days
Revision Changes Path
1.642 +37 -7 src/sys/kern/vfs_subr.c
Approved by: re (scottl)
Revision Changes Path
1.635.2.4 +46 -7 src/sys/kern/vfs_subr.c
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