From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vivek Goyal Subject: Re: [PATCH 4/4] blkcg: use radix tree to index blkgs from blkcg Date: Fri, 20 Apr 2012 13:26:39 -0400 Message-ID: <20120420172639.GM22419@redhat.com> References: <1334878164-24788-1-git-send-email-tj@kernel.org> <1334878164-24788-5-git-send-email-tj@kernel.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1334878164-24788-5-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> 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, ctalbott-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, rni-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Thu, Apr 19, 2012 at 04:29:24PM -0700, Tejun Heo wrote: > blkg lookup is currently performed by traversing linked list anchored > at blkcg->blkg_list. This is very unscalable and with blk-throttle > enabled and enough request queues on the system, this can get very > ugly quickly (blk-throttle performs look up on every bio submission). > > This patch makes blkcg use radix tree to index blkgs combined with > simple last-looked-up hint. This is mostly identical to how icqs are > indexed from ioc. > > Note that because __blkg_lookup() may be invoked without holding queue > lock, hint is only updated from __blkg_lookup_create(). Due to cfq's > cfqq caching, this makes hint updates overly lazy. This will be > improved with scheduled blkcg aware request allocation. > > Signed-off-by: Tejun Heo > Cc: Vivek Goyal Nice to see radix tree lookup and caching hint. Helps with scalability. Acked-by: Vivek Goyal Vivek