From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [patch] nd_blk,nd_pmem,nd_btt: add endio blktrace events Date: Thu, 10 Nov 2016 11:33:33 -0800 Message-ID: <20161110193333.GA10865@infradead.org> References: <20161109191715.GA20314@infradead.org> <20161109193441.GA17343@infradead.org> 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: Jeff Moyer Cc: Christoph Hellwig , "Dan J. Williams" , linux-nvdimm@ml01.01.org, linux-block@vger.kernel.org List-Id: linux-nvdimm@lists.01.org On Wed, Nov 09, 2016 at 02:43:58PM -0500, Jeff Moyer wrote: > But on the issue side, we have different trace actions: Q vs. I. On the > completion side, we just have C. You'd end up getting two C events for > each Q, and that may confuse existing utilities (such as blkparse, btt, > iowatcher, fio, etc), not to mention any scripts built around the > tracepoints, and any users looking at the raw blkparse output. > > So, are you suggesting we add another action on the endio side? If so, > that's a different patch set. ;-) If you're suggesting this multiple C > event thing, I'm not on board with that. Ok, good point. It's a little bit annoying how asymetic the tracepoints are, but fixing it now might cause more harm than it helps. That being said, it might still be a good idea to have bio_endio call the tracepoint, we'll just need a __bio_endio to bypass the tracepoints for calls from the request layer. That way all bio-based drivers will automatically do the right thing.