On Fri, Nov 11, 2016 at 09:55:10AM -0500, Jeff Moyer wrote: > Christoph Hellwig <hch@xxxxxxxxxxxxx> writes: > > > 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. > > OK, I'll look into that. I'm also still trying to decide whether a > separate endio event would be useful. Any opinions on that are welcome. > It could show up in blkparse as 'E'. For btt, I guess we could add a > Q2E column. I'm not sure C2E would ever be interesting, but maybe? FWIW I think BRD has this same issue where we get block_bio_queue tracepoint events but not block_bio_complete. Solving this in bio_endio() would fix that driver as well. Where does the Q (bio enqueue), I (req insert), etc. naming show up? Looking at a tracepoint trace in perf I don't see that naming. Is that just a short hand used between developers, or is it something else? -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
