Subject: CVS commit: src/sys/kern
To: None <source-changes@NetBSD.org>
From: Thor Lancelot Simon <email@example.com>
Date: 02/11/2004 17:36:31
Module Name: src
Committed By: tls
Date: Wed Feb 11 17:36:31 UTC 2004
Fix bug noted by firstname.lastname@example.org: the UVM free target is in *pages*,
so the last change has us comparing pages to bytes instead of pages
to buffers! The consequence was to try to free radically less memory
than UVM wanted us to -- though always at least one buffer, which is
probably why the results weren't dire.
This does suggest that buf_canrelease() could be a *lot* more
conservative about how much to release than "2 * page deficit". In
fact, serious trouble seems to ensue if it's not -- when anything
else on the system demands enough pages, we slam down to the low
water mark nd stay there. I've adjusted it to use min(page defecit,
buffer memory / 16), which still isn't quite right but seems better.
Another change: consider the case of an infinite loop that does
"tar xzf pkgsrc.tar.gz ; rm -rf pkgsrc". Each time the rm runs,
all the dead metadata will go on the AGE list -- and, until we hit
the high-water mark, stay there, at which point it may be slowly
recycled. Two adjustments seem to solve this: 1) whack buf_lotsfree()
to return 0 if there's anything on the AGE list; 2) whack buf_canrelease()
to count the memory used by the AGE list and always return at least
This basically turns the AGE list into a "delayed free" list, since we
can't entirely eliminate it as we can't free pool items from interrupt
context (e.g. from biodone()).
To consider: with the bookkeeping corrected, should buf_drain() move
back to the _end_ of the pagedaemon, and should the calculation then
try to give back at least the current defecit?
To generate a diff of this commit:
cvs rdiff -r1.114 -r1.115 src/sys/kern/vfs_bio.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.