CVS commit: src/sys/kern

["Jean-Yves Migeon" <jym%netbsd.org@localhost>]

Module Name:    src
Committed By:   jym
Date:           Tue Jun  5 22:28:11 UTC 2012

Modified Files:
        src/sys/kern: subr_pool.c

Log Message:
As pool reclaiming is unlikely to happen at interrupt or softint
context, re-enable the portion of code that allows invalidation of CPU-bound
pool caches.

Two reasons:
- CPU cached objects being invalidated, the probability of fetching an
obsolete object from the pool_cache(9) is greatly reduced. This speeds up
pool_cache_get() quite a bit as it does not have to keep destroying objects
until it finds an updated one when an invalidation is in progress.

- for situations where we have to ensure that no obsolete object remains
after a state transition (canonical example: pmap mappings between Xen VM
restoration), invalidating all pool_cache(9) is the safest way to go.

As it uses xcall(9) to broadcast the execution of pool_cache_transfer(),
pool_cache_invalidate() cannot be called from interrupt or softint context
(scheduling a xcall(9) can put a LWP to sleep).

pool_cache_xcall() => pool_cache_transfer() to reflect its use.

Invalidation being a costly process (1000s objects may be destroyed),
all places where pool_cache_invalidate() may be called from
interrupt/softint context will now get caught by the proper KASSERT(), and
fixed. Ping me when you see one.

Tested under i386 and amd64 by running ATF suite within 64MiB HVM
domains (tried triggering pgdaemon a few times).

No objection on tech-kern@.

XXX a similar fix has to be pulled up to NetBSD-6, but with a more
conservative approach.

See http://mail-index.netbsd.org/tech-kern/2012/05/29/msg013245.html


To generate a diff of this commit:
cvs rdiff -u -r1.195 -r1.196 src/sys/kern/subr_pool.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.