Author: mjg
Date: Tue Jun 9 14:16:18 2020
New Revision: 361965
URL: https://svnweb.freebsd.org/changeset/base/361965
Log:
vm: rework swap_pager_status to execute in constant time
The lock-protected iteration is trivially avoidable.
This removes a serialisation point from Linux binaries (which end up calling
here from the sysinfo syscall).
Modified:
head/sys/vm/swap_pager.c
Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c Tue Jun 9 09:42:39 2020 (r361964)
+++ head/sys/vm/swap_pager.c Tue Jun 9 14:16:18 2020 (r361965)
@@ -2541,16 +2541,10 @@ swapoff_all(void)
void
swap_pager_status(int *total, int *used)
{
- struct swdevt *sp;
- *total = 0;
- *used = 0;
- mtx_lock(&sw_dev_mtx);
- TAILQ_FOREACH(sp, &swtailq, sw_list) {
- *total += sp->sw_nblks;
- *used += sp->sw_used;
- }
- mtx_unlock(&sw_dev_mtx);
+ *total = swap_total;
+ *used = swap_total - swap_pager_avail -
+ nswapdev * howmany(BBSIZE, PAGE_SIZE);
}
int
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