From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH] Revert "libceph: use memalloc flags for net IO" Date: Tue, 07 Apr 2015 10:41:53 -0500 Message-ID: <5523FAC1.9050403@redhat.com> References: <1428414024-47769-1-git-send-email-idryomov@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:60670 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755483AbbDGPoG (ORCPT ); Tue, 7 Apr 2015 11:44:06 -0400 In-Reply-To: <1428414024-47769-1-git-send-email-idryomov@gmail.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Ilya Dryomov , ceph-devel@vger.kernel.org Cc: Mike Christie , Mel Gorman , Sage Weil On 04/07/2015 08:40 AM, Ilya Dryomov wrote: > This reverts commit 89baaa570ab0b476db09408d209578cfed700e9f. > > Dirty page throttling should be sufficient for us in the general case > so there is no need to use __GFP_MEMALLOC - it would be needed only in > the swap-over-rbd case, which we currently don't support. (It would > probably take approximately the commit that is being reverted to add > that support, but we would also need the "swap" option to distinguish > from the general case and make sure swap ceph_client-s aren't shared > with anything else.) See ceph-devel threads [1] and [2] for the > details of why enabling pfmemalloc reserves for all cases is a bad > thing. > > On top of potential system lockups related to drained emergency > reserves, this turned out to cause ceph lockups in case peers are on > the same host and communicating via loopback due to sk_filter() > dropping pfmemalloc skbs on the receiving side because the receiving > loopback socket is not tagged with SOCK_MEMALLOC. > > [1] "SOCK_MEMALLOC vs loopback" > http://www.spinics.net/lists/ceph-devel/msg22998.html > [2] "[PATCH] libceph: don't set memalloc flags in loopback case" > http://www.spinics.net/lists/ceph-devel/msg23392.html > > Conflicts: > net/ceph/messenger.c [ context: tcp_nodelay option ] > > Cc: Mike Christie > Cc: Mel Gorman > Cc: Sage Weil > Cc: stable@vger.kernel.org # 3.18+, needs backporting > Signed-off-by: Ilya Dryomov Yeah, I misunderstood the memalloc flag use. Reviewed-by: Mike Christie