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 93DD9129A63; Tue, 23 Jan 2024 00:12:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705968729; cv=none; b=f5RqyRTzBvS3QpSMNbn+30mEmVvXA00ixyoGfIBmpr+eeqX+AqIIlN9I6szckomMzjKcGfFS48i0Gcdeu1Nup/vekha//sjcOB91URccf7OUPotWtIAUlPHvme+VgaGn/IIdPqx2bGL+fS1R7PiS3Oj2p/gBKlikUPY4G5Ld9y0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705968729; c=relaxed/simple; bh=4ttioyCrV43EPU4fLErzTtJIZYwpK3LJQE5kE7FRCoU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lklZZzcmh/nZw9HX4PG06bLwzZk+sMyt0wg/GkVn24dZjLP83yxLAdN/3pXdaMuJ3vocBF9Mifqmvk2NKYbl9Dmie0WVjjXvPVCebh+lITlUDzRSl8fni97w9pzJgg4UhXVr8R9W+AJWJ+CvlaqJgZFnU2qwaaXLhZM/wdb8KEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QY7STQK/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="QY7STQK/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54433C43390; Tue, 23 Jan 2024 00:12:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1705968729; bh=4ttioyCrV43EPU4fLErzTtJIZYwpK3LJQE5kE7FRCoU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QY7STQK/+pebef0WJ2p9PwBWpZX5n2sRtdit3T4piAz9gNMuFzJENWj+Cf9mG15L8 kOXf/knhhAkqf8YWPvGQCmSFNd+Fm6TgFePt8gTqmiqmk6dcVpU1+gpirNZgZRRw4t wqdu9SwaATVGmj8EQ69CCmKNLXwS1I7V+h2s+/xI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Douglas Anderson , Judy Hsiao , David Ahern , Eric Dumazet , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 019/194] neighbour: Dont let neigh_forced_gc() disable preemption for long Date: Mon, 22 Jan 2024 15:55:49 -0800 Message-ID: <20240122235720.042209447@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240122235719.206965081@linuxfoundation.org> References: <20240122235719.206965081@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ 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 9d631b7adb7b..e571007d083c 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