From 6cafb12dc85a5bdc722791cc5070968413264909 Mon Sep 17 00:00:00 2001 From: Mark McLoughlin Date: Sat, 24 Oct 2009 14:14:31 +0200 Subject: block: silently error unsupported empty barriers too With 2.6.32-rc5 in a KVM guest using dm and virtio_blk, we see the following errors: end_request: I/O error, dev vda, sector 0 end_request: I/O error, dev vda, sector 0 The errors go away if dm stops submitting empty barriers, by reverting: commit 52b1fd5a27c625c78373e024bf570af3c9d44a79 Author: Mikulas Patocka dm: send empty barriers to targets in dm_flush We should silently error all barriers, even empty barriers, on devices like virtio_blk which don't support them. See also: https://bugzilla.redhat.com/514901 Signed-off-by: Mark McLoughlin Signed-off-by: Mike Snitzer Acked-by: Alasdair G Kergon Acked-by: Mikulas Patocka Cc: Rusty Russell Cc: Neil Brown Cc: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'block') diff --git a/block/blk-core.c b/block/blk-core.c index ac0fa10f8fa..71da5111120 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1161,7 +1161,7 @@ static int __make_request(struct request_queue *q, struct bio *bio) const unsigned int ff = bio->bi_rw & REQ_FAILFAST_MASK; int rw_flags; - if (bio_rw_flagged(bio, BIO_RW_BARRIER) && bio_has_data(bio) && + if (bio_rw_flagged(bio, BIO_RW_BARRIER) && (q->next_ordered == QUEUE_ORDERED_NONE)) { bio_endio(bio, -EOPNOTSUPP); return 0; -- cgit v1.2.3 From e6ec4fe24572ee265723d895ec4159e5559c8266 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 3 Nov 2009 20:21:35 +0100 Subject: cfq-iosched: fix bad return value cfq_should_preempt() Commit a6151c3a5c8e1ff5a28450bc8d6a99a2a0add0a7 inadvertently reversed a preempt condition check, potentially causing a performance regression. Make the meta check correct again. Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'block') diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 069a61017c0..5802e322b7a 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2051,7 +2051,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, * it's a metadata request and the current queue is doing regular IO. */ if (rq_is_meta(rq) && !cfqq->meta_pending) - return false; + return true; /* * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice. -- cgit v1.2.3 From 4b27e1bb442e964903f8a3fa6bdf33a602dc0941 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Tue, 3 Nov 2009 20:25:02 +0100 Subject: cfq-iosched: limit coop preemption CFQ has an optimization for cooperated applications. if several io-context have close requests, they will get boost. But the optimization get abused. Considering thread a, b, which work on one file. a reads sectors s, s+2, s+4, ...; b reads sectors s+1, s+3, s +5, ... Both a and b are sequential read, so they can open idle window. a reads a sector s and goes to idle window and wakeup b. b reads sector s+1, since in current implementation, cfq_should_preempt() thinks a and b are cooperators, b will preempt a. b then reads sector s+1 and goes to idle window and wakeup a. for the same reason, a will preempt b and reads s+2. a and b will continue the circle. The circle will be very long, and a and b will occupy whole disk queue. Other applications will nearly have no chance to run. Fix this limiting coop preempt until a queue is scheduled normally again. Signed-off-by: Shaohua Li Acked-by: Jeff Moyer Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'block') diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 5802e322b7a..aa1e9535e35 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -196,6 +196,7 @@ enum cfqq_state_flags { CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */ CFQ_CFQQ_FLAG_sync, /* synchronous queue */ CFQ_CFQQ_FLAG_coop, /* has done a coop jump of the queue */ + CFQ_CFQQ_FLAG_coop_preempt, /* coop preempt */ }; #define CFQ_CFQQ_FNS(name) \ @@ -222,6 +223,7 @@ CFQ_CFQQ_FNS(prio_changed); CFQ_CFQQ_FNS(slice_new); CFQ_CFQQ_FNS(sync); CFQ_CFQQ_FNS(coop); +CFQ_CFQQ_FNS(coop_preempt); #undef CFQ_CFQQ_FNS #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \ @@ -945,10 +947,13 @@ static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd, { if (!cfqq) { cfqq = cfq_get_next_queue(cfqd); - if (cfqq) + if (cfqq && !cfq_cfqq_coop_preempt(cfqq)) cfq_clear_cfqq_coop(cfqq); } + if (cfqq) + cfq_clear_cfqq_coop_preempt(cfqq); + __cfq_set_active_queue(cfqd, cfqq); return cfqq; } @@ -2066,8 +2071,16 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, * if this request is as-good as one we would expect from the * current cfqq, let it preempt */ - if (cfq_rq_close(cfqd, rq)) + if (cfq_rq_close(cfqd, rq) && (!cfq_cfqq_coop(new_cfqq) || + cfqd->busy_queues == 1)) { + /* + * Mark new queue coop_preempt, so its coop flag will not be + * cleared when new queue gets scheduled at the very first time + */ + cfq_mark_cfqq_coop_preempt(new_cfqq); + cfq_mark_cfqq_coop(new_cfqq); return true; + } return false; } -- cgit v1.2.3