From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 1/2] block: introduce polling on bio level Date: Thu, 30 Jan 2020 22:35:27 -0800 Message-ID: <20200131063527.GC6267@infradead.org> References: <20200126044138.5066-1-andrzej.jakowski@linux.intel.com> <20200126044138.5066-2-andrzej.jakowski@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-block-owner@vger.kernel.org To: Jens Axboe Cc: Andrzej Jakowski , song@kernel.org, linux-block@vger.kernel.org, linux-raid@vger.kernel.org, Artur Paszkiewicz List-Id: linux-raid.ids On Wed, Jan 29, 2020 at 09:01:49PM -0700, Jens Axboe wrote: > blk_poll() used to be a pointer in the queue, but since we just had > one implementation, we got rid of it. Might make sense to > reintroduce that, and just make it an optimized indirect call. I > think that would be prettier than add the bio hack in the middle of > it, and you're having to add a queue pointer anyway. Well, the other reason is to avoid an indirect call for the blk-mq case, which are fairly expensive. In fact I'm pretty sure we avoid indirect calls from the bio layer into blk-mq entirely for the fast path at the moment, and it would be great to keep it that way.