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From: zhenwei pi <pizhenwei@bytedance.com>
To: linux-kernel@vger.kernel.org,
	linux-mm@kvack.org,
	virtualization@lists.linux.dev
Cc: mst@redhat.com,
	david@redhat.com,
	jasowang@redhat.com,
	xuanzhuo@linux.alibaba.com,
	akpm@linux-foundation.org,
	zhenwei pi <pizhenwei@bytedance.com>
Subject: [RFC 1/3] virtio_balloon: introduce oom-kill invocations
Date: Mon, 15 Apr 2024 16:41:11 +0800
Message-Id: <20240415084113.1203428-2-pizhenwei@bytedance.com>
In-Reply-To: <20240415084113.1203428-1-pizhenwei@bytedance.com>
References: <20240415084113.1203428-1-pizhenwei@bytedance.com>
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When the guest OS runs under critical memory pressure, the guest
starts to kill processes. A guest monitor agent may scan 'oom_kill'
from /proc/vmstat, and reports the OOM KILL event. However, the agent
may be killed and we will loss this critical event(and the later
events).

For now we can also grep for magic words in guest kernel log from host
side. Rather than this unstable way, virtio balloon reports OOM-KILL
invocations instead.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
 drivers/virtio/virtio_balloon.c     | 2 ++
 include/uapi/linux/virtio_balloon.h | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 1f5b3dd31fcf..fd8daa742734 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -352,6 +352,8 @@ static unsigned int update_balloon_stats(struct virtio_balloon *vb)
 				pages_to_bytes(available));
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
 				pages_to_bytes(caches));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_OOM_KILL,
+				events[OOM_KILL]);
 
 	return idx;
 }
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index ddaa45e723c4..cde5547e64a7 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -71,7 +71,8 @@ struct virtio_balloon_config {
 #define VIRTIO_BALLOON_S_CACHES   7   /* Disk caches */
 #define VIRTIO_BALLOON_S_HTLB_PGALLOC  8  /* Hugetlb page allocations */
 #define VIRTIO_BALLOON_S_HTLB_PGFAIL   9  /* Hugetlb page allocation failures */
-#define VIRTIO_BALLOON_S_NR       10
+#define VIRTIO_BALLOON_S_OOM_KILL      10 /* OOM killer invocations */
+#define VIRTIO_BALLOON_S_NR       11
 
 #define VIRTIO_BALLOON_S_NAMES_WITH_PREFIX(VIRTIO_BALLOON_S_NAMES_prefix) { \
 	VIRTIO_BALLOON_S_NAMES_prefix "swap-in", \
@@ -83,7 +84,8 @@ struct virtio_balloon_config {
 	VIRTIO_BALLOON_S_NAMES_prefix "available-memory", \
 	VIRTIO_BALLOON_S_NAMES_prefix "disk-caches", \
 	VIRTIO_BALLOON_S_NAMES_prefix "hugetlb-allocations", \
-	VIRTIO_BALLOON_S_NAMES_prefix "hugetlb-failures" \
+	VIRTIO_BALLOON_S_NAMES_prefix "hugetlb-failures", \
+	VIRTIO_BALLOON_S_NAMES_prefix "oom-kill" \
 }
 
 #define VIRTIO_BALLOON_S_NAMES VIRTIO_BALLOON_S_NAMES_WITH_PREFIX("")
-- 
2.34.1