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Message-ID: <20231218124656.1381949-4-sashal@kernel.org>
Date: Mon, 18 Dec 2023 07:46:49 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Cc: Judy Hsiao <judyhsiao@...omium.org>,
Douglas Anderson <dianders@...omium.org>,
David Ahern <dsahern@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
"David S . Miller" <davem@...emloft.net>,
Sasha Levin <sashal@...nel.org>,
kuba@...nel.org,
pabeni@...hat.com,
martin.lau@...nel.org,
ja@....bg,
joel.granados@...il.com,
leon@...nel.org,
haleyb.dev@...il.com,
netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 4/7] neighbour: Don't let neigh_forced_gc() disable preemption for long
From: Judy Hsiao <judyhsiao@...omium.org>
[ Upstream commit e5dc5afff62f3e97e86c3643ec9fcad23de4f2d3 ]
We are seeing cases where neigh_cleanup_and_release() is called by
neigh_forced_gc() many times in a row with preemption turned off.
When running on a low powered CPU at a low CPU frequency, this has
been measured to keep preemption off for ~10 ms. That's not great on a
system with HZ=1000 which expects tasks to be able to schedule in
with ~1ms latency.
Suggested-by: Douglas Anderson <dianders@...omium.org>
Signed-off-by: Judy Hsiao <judyhsiao@...omium.org>
Reviewed-by: David Ahern <dsahern@...nel.org>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Reviewed-by: Douglas Anderson <dianders@...omium.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
net/core/neighbour.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 9d631b7adb7bf..e571007d083cc 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -226,9 +226,11 @@ static int neigh_forced_gc(struct neigh_table *tbl)
{
int max_clean = atomic_read(&tbl->gc_entries) -
READ_ONCE(tbl->gc_thresh2);
+ u64 tmax = ktime_get_ns() + NSEC_PER_MSEC;
unsigned long tref = jiffies - 5 * HZ;
struct neighbour *n, *tmp;
int shrunk = 0;
+ int loop = 0;
NEIGH_CACHE_STAT_INC(tbl, forced_gc_runs);
@@ -251,11 +253,16 @@ static int neigh_forced_gc(struct neigh_table *tbl)
shrunk++;
if (shrunk >= max_clean)
break;
+ if (++loop == 16) {
+ if (ktime_get_ns() > tmax)
+ goto unlock;
+ loop = 0;
+ }
}
}
WRITE_ONCE(tbl->last_flush, jiffies);
-
+unlock:
write_unlock_bh(&tbl->lock);
return shrunk;
--
2.43.0
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