On Thu 03-03-11 21:31:19, Wu Fengguang wrote: > On Thu, Mar 03, 2011 at 10:26:19AM +0800, Jun'ichi Nomura wrote: > > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899962 + 8 > > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899970 + 8 > > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899978 + 8 > > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899986 + 8 > > flush-8:0-2743 4606: block_bio_queue: 8,0 W 94899994 + 8 > ==> > kworker/0:1-11 4606: block_rq_issue: 8,0 W 0 () 94899962 + 40 > > >> flush-8:0-2743 4606: block_bio_queue: 8,0 W 94898554 + 8 > ==> > >> flush-8:0-2743 4606: block_rq_issue: 8,0 W 0 () 94898554 + 8 > > I'd expect the wrapped around 94898554+8 to be merged with 94899962+8. How could they be merged? They are not continguous... > Why kworker/0:1-11 is submitting the request early? And the second > request is submitted by flush-8:0-2743. I'm not sure about that either - but I think that kworker is submitting the work when unplug happens while flush ends up doing it when the queue is alredy unplugged. > > The 1st writeback ended at block 94898562. (94898554+8) > > The 2nd writeback started there. > > However, since the last page at the 1st writeback was just redirtied, > > the 2nd writeback looped back to block 94898554 after sequentially > > submitting blocks from 94898562 to 94900001. > > > > 1 extra seek which could be avoided. > > I haven't seen fatal problem with the latest kernel, though. > > > > With older kernels (before 2.6.29, without commit 31a12666), > > kupdate leaves the dirty pages like spots until the application wraps > > around the ring. (It could take hours to days.) > > That led me to this code. > > > > > But as I'm thinking about it, it wouldn't harm our original aim to do > > > what you propose and it can help this relatively common case. So I think > > > it's a good idea. Fengguang, what do you think? > > I see no problem too. > > Tested-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> OK, I'll update the changelog to reflect our discussion and post the patch to Andrew for inclusion. Honza -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
