git: DragonFly_RELEASE_6_2 kernel - vnode recycling, intermediate fix
dillon at crater.dragonflybsd.org
Sat Apr 30 17:43:26 PDT 2022
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date: Fri Apr 29 16:46:09 2022 -0700
kernel - vnode recycling, intermediate fix
* Fix a condition where vnlru (the vnode recycler) can live-
lock on unsuitable vnodes in the inactive list and stop
making progress, causing the system to block.
First, don't deactivate vnodes which the inactive scan won't
recycle. Vnodes which are in the namecache topology but not
at a leaf won't be recycled by the vnlru thread. Leave these
vnodes on the active queue. This prevents the inactive queue
from filling up with vnodes that it can't recycle.
Second, the active scan in vnlru() will now call
cache_inval_vp_quick() to attempt to make a vnode presentable
so it can be deactivated. The inactive scan also does the same
thing, because some leakage can happen anyway.
* The active scan should be able to make continuous progress
as successful cache_inval_vp_quick() calls make more and more
vnodes presentable that might have previously been internal nodes
in the namecache topology. So the active scan should be able to
achieve the desired balance between the active and inactive queue.
* This should also improve performance when constant recycling
is happening by moving more of the work to the active->inactive
transition and doing less work in the inactive->free
* Add cache_inval_vp_quick(), a function which attempts to trivially
disassociate a vnode from the namecache topology and will handle
any direct children if the vnode is not at a leaf (but not recursively
on its own). The definition of 'trivially' for the children are
namecache records that can be locked non-blocking, have no additional
refs, and do not record a vnode.
* Cleanup cache_unlink_parent(). Have cache_zap() use this
function instead of rerolling the same code. The cache_rename()
code winds up being slightly more complex. And now
cache_inval_vp_quick() can use the function too.
Summary of changes:
sys/kern/vfs_cache.c | 258 ++++++++++++++++++++++++++++++++-------------------
sys/kern/vfs_lock.c | 81 ++++++++++++++--
sys/kern/vfs_mount.c | 2 +-
sys/sys/namecache.h | 1 +
4 files changed, 240 insertions(+), 102 deletions(-)
DragonFly BSD source repository
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