From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70D8E83539; Mon, 18 Dec 2023 12:47:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pqddNTbs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60B55C433C8; Mon, 18 Dec 2023 12:47:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702903627; bh=+OVnW9vNlawrZz1istndX1LrRMdDvVBnU24JfXpxuPY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pqddNTbs5ghWquCMmYw2ajxJhifTnkKN1j92poqObsQ/JMsdHCZo2YUlh8Cvtj2m5 xBsXcYRPXaz03zKbbIlVf5qR9ahJNfaX0FcpOsV8ND91k/pSXdYyeIY8rsruNCsYGN FEOlfp8qIjXwHZhcmzL4dwtPfbtvHXE1rfJHiD/2dIEv0GXQdQcdceNEH7TueU3GNC 2yHjFrhP061PvlvFVBQLawZhTZviEYjNoCiMhlaxxsUFVfgAwDh+tp8JKYqNsaQySN 6CRZHSxragdLBbF0o8EWQKS3jxLtaQcE/SD4o8SXiwe3vmcrAgtXhz3K6Ur64EYgQO /qLa76TP9g+YA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Judy Hsiao , Douglas Anderson , David Ahern , Eric Dumazet , "David S . Miller" , Sasha Levin , kuba@kernel.org, pabeni@redhat.com, martin.lau@kernel.org, ja@ssi.bg, joel.granados@gmail.com, leon@kernel.org, haleyb.dev@gmail.com, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 5.4 4/7] neighbour: Don't let neigh_forced_gc() disable preemption for long Date: Mon, 18 Dec 2023 07:46:49 -0500 Message-ID: <20231218124656.1381949-4-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231218124656.1381949-1-sashal@kernel.org> References: <20231218124656.1381949-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.4.264 Content-Transfer-Encoding: 8bit From: Judy Hsiao [ 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 Signed-off-by: Judy Hsiao Reviewed-by: David Ahern Reviewed-by: Eric Dumazet Reviewed-by: Douglas Anderson Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- 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