Patch "flowcache: Increase threshold for refusing new allocations" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

flowcache: Increase threshold for refusing new allocations

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
flowcache-increase-threshold-for-refusing-new-allocations.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Miroslav Urbanek <[email protected]>
Date: Mon, 21 Nov 2016 15:48:21 +0100
Subject: flowcache: Increase threshold for refusing new allocations
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From: Miroslav Urbanek <[email protected]>

commit 6b226487815574193c1da864f2eac274781a2b0c upstream.

The threshold for OOM protection is too small for systems with large number of CPUs. Applications report ENOBUFs on connect() every 10 minutes.

The problem is that the variable net->xfrm.flow_cache_gc_count is a global counter while the variable fc->high_watermark is a per-CPU constant. Take the number of CPUs into account as well.

---
 net/core/flow.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

@@ -95,7 +95,6 @@ static void flow_cache_gc_task(struct wo
 	list_for_each_entry_safe(fce, n, &gc_list, u.gc_list) {
 		flow_entry_kill(fce, xfrm);
 		atomic_dec(&xfrm->flow_cache_gc_count);
-		WARN_ON(atomic_read(&xfrm->flow_cache_gc_count) < 0);
 	}
 }
 

@@ -236,9 +235,8 @@ flow_cache_lookup(struct net *net, const
 		if (fcp->hash_count > fc->high_watermark)
 			flow_cache_shrink(fc, fcp);
 
-		if (fcp->hash_count > 2 * fc->high_watermark ||
-		    atomic_read(&net->xfrm.flow_cache_gc_count) > fc->high_watermark) {
-			atomic_inc(&net->xfrm.flow_cache_genid);
+		if (atomic_read(&net->xfrm.flow_cache_gc_count) >
+		    2 * num_online_cpus() * fc->high_watermark) {
 			flo = ERR_PTR(-ENOBUFS);
 			goto ret_object;
 		}

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/flowcache-increase-threshold-for-refusing-new-allocations.patch