git: 4a864f624a70 - main - vm_pageout: Print a more accurate message to the console before an OOM kill

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=4a864f624a7097f1d032a0350ac70fa6c371179e

commit 4a864f624a7097f1d032a0350ac70fa6c371179e
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-01-14 20:03:53 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-01-14 20:04:21 +0000

    vm_pageout: Print a more accurate message to the console before an OOM kill
    
    Previously we'd always print "out of swap space."  This can be
    misleading, as there are other reasons an OOM kill can be triggered.  In
    particular, it's entirely possible to trigger an OOM kill on a system
    with plenty of free swap space.
    
    Reviewed by:    kib
    MFC after:      2 weeks
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D33810
---
 sys/vm/vm_pageout.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 899d35cd43b6..36d5f3275800 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1902,6 +1902,7 @@ static struct mtx vm_oom_ratelim_mtx;
 void
 vm_pageout_oom(int shortage)
 {
+	const char *reason;
 	struct proc *p, *bigproc;
 	vm_offset_t size, bigsize;
 	struct thread *td;
@@ -2014,11 +2015,25 @@ vm_pageout_oom(int shortage)
 		}
 	}
 	sx_sunlock(&allproc_lock);
+
 	if (bigproc != NULL) {
+		switch (shortage) {
+		case VM_OOM_MEM:
+			reason = "failed to reclaim memory";
+			break;
+		case VM_OOM_MEM_PF:
+			reason = "a thread waited too long to allocate a page";
+			break;
+		case VM_OOM_SWAPZ:
+			reason = "out of swap space";
+			break;
+		default:
+			panic("unknown OOM reason %d", shortage);
+		}
 		if (vm_panic_on_oom != 0 && --vm_panic_on_oom == 0)
-			panic("out of swap space");
+			panic("%s", reason);
 		PROC_LOCK(bigproc);
-		killproc(bigproc, "out of swap space");
+		killproc(bigproc, reason);
 		sched_nice(bigproc, PRIO_MIN);
 		_PRELE(bigproc);
 		PROC_UNLOCK(bigproc);