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Prevent ticks rollover from preventing vm_lowmem event

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Currently vm_pageout_scan() uses a ticks-based scheme to rate-limit
the number of times that the vm_lowmem event will happen.  However
if no events happen for long enough for ticks to roll over, this
leaves us in a long window in which vm_lowmem events will not
happen.

Replace the use of ticks with time_t to prevent rollover from ever
being an issue.

Reviewed by:	ian
MFC after:	3 weeks
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D3439
This commit is contained in:
Ryan Stone 2015-08-20 20:28:51 +00:00
parent e178d0d43e
commit a6bf3a9ef6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=286970
1 changed files with 4 additions and 3 deletions
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7
sys/vm/vm_pageout.c
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@ -93,6 +93,7 @@ __FBSDID("$FreeBSD$");
#include <sys/sdt.h>
#include <sys/signalvar.h>
#include <sys/smp.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/rwlock.h>
@ -171,7 +172,7 @@ static int vm_pageout_update_period;
static int defer_swap_pageouts;
static int disable_swap_pageouts;
static int lowmem_period = 10;
static int lowmem_ticks;
static time_t lowmem_uptime;
#if defined(NO_SWAPPING)
static int vm_swap_enabled = 0;
@ -1034,7 +1035,7 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
* some. We rate limit to avoid thrashing.
*/
if (vmd == &vm_dom[0] && pass > 0 &&
(ticks - lowmem_ticks) / hz >= lowmem_period) {
(time_uptime - lowmem_uptime) >= lowmem_period) {
/*
* Decrease registered cache sizes.
*/
@ -1045,7 +1046,7 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
* drained above.
*/
uma_reclaim();
lowmem_ticks = ticks;
lowmem_uptime = time_uptime;
}
/*