When considering the amount of free pages in the page daemon a small
amount is always kept for the buffer cache... except in one place.
The diff below gets rid of this exception. This is important because
uvmpd_scan() is called conditionally using the following check:
if (uvmexp.free - BUFPAGES_DEFICIT) < uvmexp.freetarg) {
...
}
So in case of swap shortage we might end up freeing fewer pages than
wanted.
ok?
Index: uvm/uvm_pdaemon.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_pdaemon.c,v
retrieving revision 1.98
diff -u -p -r1.98 uvm_pdaemon.c
--- uvm/uvm_pdaemon.c 4 May 2022 14:58:26 -0000 1.98
+++ uvm/uvm_pdaemon.c 5 May 2022 13:40:28 -0000
@@ -923,12 +923,13 @@ uvmpd_scan(void)
* detect if we're not going to be able to page anything out
* until we free some swap resources from active pages.
*/
+ free = uvmexp.free - BUFPAGES_DEFICIT;
swap_shortage = 0;
- if (uvmexp.free < uvmexp.freetarg &&
+ if (free < uvmexp.freetarg &&
uvmexp.swpginuse == uvmexp.swpages &&
!uvm_swapisfull() &&
pages_freed == 0) {
- swap_shortage = uvmexp.freetarg - uvmexp.free;
+ swap_shortage = uvmexp.freetarg - free;
}
for (p = TAILQ_FIRST(&uvm.page_active);
