On 5/11/22 12:52, Mark Millard wrote:
Relative to avoiding hang-ups, so far it seems that
use of vm.swap_enabled=0 with vm.swap_idle_enabled=0
makes hang-ups less likely/less frequent/harder to
produce examples of. But is no guarantee of lack of
a hang-up. Its does change the cause of the hang-up
(in that it avoids processes with kernel stacks swapped
out being involved).
thanks for the above analysis Mark. i am going to test these settings
out now as i'm still seeing the lockup.
this most recent hang-up was using a patch tijl@ asked me to test
(attached to this email), and the default setting of vm.pageout_oom_seq:
12. interestingly enough with the patch applied i observed a smaller
amount of memory used for laundry as well as less swap space used until
right before the crash.
cheers,
-p
--
Pete Wright
p...@nomadlogic.org
@nomadlogicLA
From f3260a2eb1cdc86f9216b7923d7b09704a37e79d Mon Sep 17 00:00:00 2001
From: Tijl Coosemans <t...@freebsd.org>
Date: Sun, 8 May 2022 12:19:28 +0200
Subject: [PATCH] vm: stop background laundering when no progress
Let vm_pageout_laundry_worker go to sleep when it cannot make
progress (nfreed == 0). This allows other threads to run so they
can hopefully free some memory.
This restores behaviour from before c098768e4dad and 60684862588f
and prevents some OOM kills.
Tested by: Pete Wright <p...@nomadlogic.org>
MFC after: 2 weeks
---
sys/vm/vm_pageout.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 36d5f3275800..fbb2cd4128f0 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1061,15 +1061,13 @@ vm_pageout_laundry_worker(void *arg)
* clean pages freed by the page daemon since the last
* background laundering. Thus, as the ratio of dirty to
* clean inactive pages grows, the amount of memory pressure
- * required to trigger laundering decreases. We ensure
- * that the threshold is non-zero after an inactive queue
- * scan, even if that scan failed to free a single clean page.
+ * required to trigger laundering decreases.
*/
trybackground:
nclean = vmd->vmd_free_count +
vmd->vmd_pagequeues[PQ_INACTIVE].pq_cnt;
ndirty = vmd->vmd_pagequeues[PQ_LAUNDRY].pq_cnt;
- if (target == 0 && ndirty * isqrt(howmany(nfreed + 1,
+ if (target == 0 && ndirty * isqrt(howmany(nfreed,
vmd->vmd_free_target - vmd->vmd_free_min)) >= nclean) {
target = vmd->vmd_background_launder_target;
}
--
2.35.1
