From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Thumshirn Subject: Re: [PATCH 06/14] block: lift setting the readahead size into the block layer Date: Wed, 22 Jul 2020 07:13:54 +0000 Message-ID: References: <20200722062552.212200-1-hch@lst.de> <20200722062552.212200-7-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: Content-Language: en-US Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christoph Hellwig , Jens Axboe Cc: Song Liu , Hans de Goede , Richard Weinberger , Minchan Kim , "linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , "linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "drbd-dev-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org" , "linux-raid-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" , "cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: dm-devel.ids On 22/07/2020 08:27, Christoph Hellwig wrote:=0A= > + q->backing_dev_info->ra_pages =3D=0A= > + max(queue_io_opt(q) * 2 / PAGE_SIZE, VM_READAHEAD_PAGES);=0A= =0A= Dumb question, wouldn't a '>> PAGE_SHIFT' be better instead of a potentiall= y =0A= costly division?=0A= =0A= Or aren't we caring at all as it's a) not in the fast-path and b) compilers= =0A= can optimize it to a shift?=0A=