From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933866AbcKMLZU (ORCPT ); Sun, 13 Nov 2016 06:25:20 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:35848 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933800AbcKMLZS (ORCPT ); Sun, 13 Nov 2016 06:25:18 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Alexei Starovoitov , Greg Thelen , Greg Rose , "David S. Miller" Subject: [PATCH 4.4 13/34] netlink: do not enter direct reclaim from netlink_dump() Date: Sun, 13 Nov 2016 12:24:45 +0100 Message-Id: <20161113112400.643624121@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161113112400.008903838@linuxfoundation.org> References: <20161113112400.008903838@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit d35c99ff77ecb2eb239731b799386f3b3637a31e ] Since linux-3.15, netlink_dump() can use up to 16384 bytes skb allocations. Due to struct skb_shared_info ~320 bytes overhead, we end up using order-3 (on x86) page allocations, that might trigger direct reclaim and add stress. The intent was really to attempt a large allocation but immediately fallback to a smaller one (order-1 on x86) in case of memory stress. On recent kernels (linux-4.4), we can remove __GFP_DIRECT_RECLAIM to meet the goal. Old kernels would need to remove __GFP_WAIT While we are at it, since we do an order-3 allocation, allow to use all the allocated bytes instead of 16384 to reduce syscalls during large dumps. iproute2 already uses 32KB recvmsg() buffer sizes. Alexei provided an initial patch downsizing to SKB_WITH_OVERHEAD(16384) Fixes: 9063e21fb026 ("netlink: autosize skb lengthes") Signed-off-by: Eric Dumazet Reported-by: Alexei Starovoitov Cc: Greg Thelen Reviewed-by: Greg Rose Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/netlink/af_netlink.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2557,7 +2557,7 @@ static int netlink_recvmsg(struct socket /* Record the max length of recvmsg() calls for future allocations */ nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len); nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len, - 16384); + SKB_WITH_OVERHEAD(32768)); copied = data_skb->len; if (len < copied) { @@ -2810,14 +2810,13 @@ static int netlink_dump(struct sock *sk) if (alloc_min_size < nlk->max_recvmsg_len) { alloc_size = nlk->max_recvmsg_len; skb = netlink_alloc_skb(sk, alloc_size, nlk->portid, - GFP_KERNEL | - __GFP_NOWARN | - __GFP_NORETRY); + (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) | + __GFP_NOWARN | __GFP_NORETRY); } if (!skb) { alloc_size = alloc_min_size; skb = netlink_alloc_skb(sk, alloc_size, nlk->portid, - GFP_KERNEL); + (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM)); } if (!skb) goto errout_skb;