From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Moyer Subject: Re: [PATCH 4.5/8] blkcg, cfq-iosched: use GFP_NOWAIT instead of GFP_ATOMIC for non-critical allocations Date: Tue, 09 Jun 2015 10:27:59 -0400 Message-ID: References: <1433753973-23684-1-git-send-email-tj@kernel.org> <20150609042131.GN21465@mtj.duckdns.org> Mime-Version: 1.0 Return-path: In-Reply-To: <20150609042131.GN21465-qYNAdHglDFBN0TnZuCh8vA@public.gmane.org> (Tejun Heo's message of "Tue, 9 Jun 2015 13:21:31 +0900") Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, avanzini.arianna-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org Tejun Heo writes: > From b848495d2c987e960d1f7794966d82c05fcefc6d Mon Sep 17 00:00:00 2001 > From: Tejun Heo > Date: Tue, 9 Jun 2015 13:19:40 +0900 > > blkcg performs several allocations to track IOs per cgroup and enforce > resource control. Most of these allocations are performed lazily on > demand in the IO path and thus can't involve reclaim path. Currently, > these allocations use GFP_ATOMIC; however, blkcg can gracefully deal > with occassional failures of these allocations by punting IOs to the > root cgroup and there's no reason to reach into the emergency reserve. > > This patch replaces GFP_ATOMIC with GFP_NOWAIT for the following > allocations. > > * bdi_writeback_congested and blkcg_gq allocations in blkg_create(). > > * radix tree node allocations for blkcg->blkg_tree. > > * cfq_queue allocation on ioprio changes. > > Signed-off-by: Tejun Heo > Suggested-by: Jeff Moyer > Suggested-by: Vivek Goyal Thanks, Tejun! Reviewed-by: Jeff Moyer