freebsd-dev/sys/sparc64
Mike Silbersack 7f3a40933b Fix a horribly suboptimal algorithm in the vm_daemon.
In order to determine what to page out, the vm_daemon checks
reference bits on all pages belonging to all processes.  Unfortunately,
the algorithm used reacted badly with shared pages; each shared page
would be checked once per process sharing it; this caused an O(N^2)
growth of tlb invalidations.  The algorithm has been changed so that
each page will be checked only 16 times.

Prior to this change, a fork/sleepbomb of 1300 processes could cause
the vm_daemon to take over 60 seconds to complete, effectively
freezing the system for that time period.  With this change
in place, the vm_daemon completes in less than a second.  Any system
with hundreds of processes sharing pages should benefit from this change.

Note that the vm_daemon is only run when the system is under extreme
memory pressure.  It is likely that many people with loaded systems saw
no symptoms of this problem until they reached the point where swapping
began.

Special thanks go to dillon, peter, and Chuck Cranor, who helped me
get up to speed with vm internals.

PR:		33542, 20393
Reviewed by:	dillon
MFC after:	1 week
2002-02-27 18:03:02 +00:00
..
compile Obrien created this directory, but I didn't cvs add cvsignore 2001-07-01 23:37:03 +00:00
conf I was able to boot this kernel using the latest WIP kernel sources. 2002-02-25 22:13:44 +00:00
ebus Minor bug fixes (add a missing break, correct the resource ranges, remove 2002-02-13 15:35:22 +00:00
include Add the following functions/macros to support byte order conversions and 2002-02-27 17:16:18 +00:00
isa Fix typos in a comment. 2002-02-13 15:43:42 +00:00
pci Merge r1.39 from NetBSD (manage both streaming caches for psycho pairs). 2002-02-13 16:07:59 +00:00
sbus Add support for the SBus, which is used in early Sun UltraSPARC machines. 2002-02-13 16:11:36 +00:00
sparc64 Fix a horribly suboptimal algorithm in the vm_daemon. 2002-02-27 18:03:02 +00:00