| Message ID | 1491307665-47656-2-git-send-email-hare@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Hannes, Thanks for taking a crack at the issue. My comments below.. On Tue, 4 Apr 2017, 5:07am, Hannes Reinecke wrote: > Most legacy HBAs have a tagset per HBA, not per queue. To map > these devices onto block-mq this patch implements a new tagset > flag BLK_MQ_F_GLOBAL_TAGS, which will cause the tag allocator > to use just one tagset for all hardware queues. > > Signed-off-by: Hannes Reinecke <hare@suse.com> > --- > block/blk-mq-tag.c | 12 ++++++++---- > block/blk-mq.c | 10 ++++++++-- > include/linux/blk-mq.h | 1 + > 3 files changed, 17 insertions(+), 6 deletions(-) > > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > index e48bc2c..a14e76c 100644 > --- a/block/blk-mq-tag.c > +++ b/block/blk-mq-tag.c > @@ -276,9 +276,11 @@ static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, > busy_tag_iter_fn *fn, void *priv) > { > - int i; > + int i, lim = tagset->nr_hw_queues; > > - for (i = 0; i < tagset->nr_hw_queues; i++) { > + if (tagset->flags & BLK_MQ_F_GLOBAL_TAGS) > + lim = 1; > + for (i = 0; i < lim; i++) { > if (tagset->tags && tagset->tags[i]) > blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv); > } > @@ -287,12 +289,14 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, > > int blk_mq_reinit_tagset(struct blk_mq_tag_set *set) > { > - int i, j, ret = 0; > + int i, j, ret = 0, lim = set->nr_hw_queues; > > if (!set->ops->reinit_request) > goto out; > > - for (i = 0; i < set->nr_hw_queues; i++) { > + if (set->flags & BLK_MQ_F_GLOBAL_TAGS) > + lim = 1; > + for (i = 0; i < lim; i++) { > struct blk_mq_tags *tags = set->tags[i]; > > for (j = 0; j < tags->nr_tags; j++) { > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 159187a..db96ed0 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2061,6 +2061,10 @@ static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx) > { > int ret = 0; > > + if ((set->flags & BLK_MQ_F_GLOBAL_TAGS) && hctx_idx != 0) { > + set->tags[hctx_idx] = set->tags[0]; > + return true; > + } So, this effectively make all request allocations to the same NUMA node locality of the hctx_idx 0, correct? Is the performance hit you were talking about in the cover letter? Do you have any other alternatives in mind? Dynamic growing/shrinking tags/request-pool in hctx with a fixed base as start? One alternative that comes to my mind is to move the divvy up logic to SCSI (instead of LLD doing it), IOW: 1. Have SCSI set tag_set.queue_depth to can_queue/nr_hw_queues 2. Have blk_mq_unique_tag() (or a new i/f) returning "hwq * nr_hw_queue + rq->tag" That would make the tags linear in the can_queue space, but could result in poor use of LLD resource if a given hctx has used up all it's tags. On a related note, would not the current use of can_queue in SCSI lead to poor resource utilization in MQ cases? Like, block layer allocating nr_hw_queues * tags+request+driver_data.etc * can_queue, but SCSI limiting the number of requests to can_queue. BTW, if you would like me to try out this patch on my setup, please let me know. Regards, -Arun > set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx, > set->queue_depth, set->reserved_tags); > if (!set->tags[hctx_idx]) > @@ -2080,8 +2084,10 @@ static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set, > unsigned int hctx_idx) > { > if (set->tags[hctx_idx]) { > - blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx); > - blk_mq_free_rq_map(set->tags[hctx_idx]); > + if (!(set->flags & BLK_MQ_F_GLOBAL_TAGS) || hctx_idx == 0) { > + blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx); > + blk_mq_free_rq_map(set->tags[hctx_idx]); > + } > set->tags[hctx_idx] = NULL; > } > } > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index b296a90..eee27b016 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -155,6 +155,7 @@ enum { > BLK_MQ_F_DEFER_ISSUE = 1 << 4, > BLK_MQ_F_BLOCKING = 1 << 5, > BLK_MQ_F_NO_SCHED = 1 << 6, > + BLK_MQ_F_GLOBAL_TAGS = 1 << 7, > BLK_MQ_F_ALLOC_POLICY_START_BIT = 8, > BLK_MQ_F_ALLOC_POLICY_BITS = 1, > >
On 04/06/2017 08:27 AM, Arun Easi wrote: > Hi Hannes, > > Thanks for taking a crack at the issue. My comments below.. > > On Tue, 4 Apr 2017, 5:07am, Hannes Reinecke wrote: > >> Most legacy HBAs have a tagset per HBA, not per queue. To map >> these devices onto block-mq this patch implements a new tagset >> flag BLK_MQ_F_GLOBAL_TAGS, which will cause the tag allocator >> to use just one tagset for all hardware queues. >> >> Signed-off-by: Hannes Reinecke <hare@suse.com> >> --- >> block/blk-mq-tag.c | 12 ++++++++---- >> block/blk-mq.c | 10 ++++++++-- >> include/linux/blk-mq.h | 1 + >> 3 files changed, 17 insertions(+), 6 deletions(-) >> >> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c >> index e48bc2c..a14e76c 100644 >> --- a/block/blk-mq-tag.c >> +++ b/block/blk-mq-tag.c >> @@ -276,9 +276,11 @@ static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, >> void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, >> busy_tag_iter_fn *fn, void *priv) >> { >> - int i; >> + int i, lim = tagset->nr_hw_queues; >> >> - for (i = 0; i < tagset->nr_hw_queues; i++) { >> + if (tagset->flags & BLK_MQ_F_GLOBAL_TAGS) >> + lim = 1; >> + for (i = 0; i < lim; i++) { >> if (tagset->tags && tagset->tags[i]) >> blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv); >> } >> @@ -287,12 +289,14 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, >> >> int blk_mq_reinit_tagset(struct blk_mq_tag_set *set) >> { >> - int i, j, ret = 0; >> + int i, j, ret = 0, lim = set->nr_hw_queues; >> >> if (!set->ops->reinit_request) >> goto out; >> >> - for (i = 0; i < set->nr_hw_queues; i++) { >> + if (set->flags & BLK_MQ_F_GLOBAL_TAGS) >> + lim = 1; >> + for (i = 0; i < lim; i++) { >> struct blk_mq_tags *tags = set->tags[i]; >> >> for (j = 0; j < tags->nr_tags; j++) { >> diff --git a/block/blk-mq.c b/block/blk-mq.c >> index 159187a..db96ed0 100644 >> --- a/block/blk-mq.c >> +++ b/block/blk-mq.c >> @@ -2061,6 +2061,10 @@ static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx) >> { >> int ret = 0; >> >> + if ((set->flags & BLK_MQ_F_GLOBAL_TAGS) && hctx_idx != 0) { >> + set->tags[hctx_idx] = set->tags[0]; >> + return true; >> + } > > So, this effectively make all request allocations to the same NUMA node > locality of the hctx_idx 0, correct? Is the performance hit you were > talking about in the cover letter? > Yes. It does make the request allocations local to NUMA node 0, but then this will only affect LLDDs which are actually _using_ NUMA locality when allocating the request nodes. However, SCSI doesn't set a NUMA node locality to begin with, so this doesn't affect us. No, what I meant is this: the 'sbitmap' allocator already splits up the bitmap into several words, which then should provide a better NUMA locality per map. When we're using a shared global map it's unclear whether the individual words of the sbitmap can and will be moved to the various NUMA nodes, or whether we suffer from non-locality. My tests so far have been inconclusive; but then I'm not happy with the testcase anyway (using null_blk I only get 250k/250k r/w IOPs, which I found rather disappointing). > Do you have any other alternatives in mind? Dynamic growing/shrinking > tags/request-pool in hctx with a fixed base as start? > > One alternative that comes to my mind is to move the divvy up logic to > SCSI (instead of LLD doing it), IOW: > > 1. Have SCSI set tag_set.queue_depth to can_queue/nr_hw_queues > 2. Have blk_mq_unique_tag() (or a new i/f) returning "hwq * nr_hw_queue + > rq->tag" > > That would make the tags linear in the can_queue space, but could result > in poor use of LLD resource if a given hctx has used up all it's tags. > Exactly. This is the method I used for implementing mq support for lpfc and mpt3sas; however the complaint there indeed was that we might be running into a tag starvation scenario with a large number of LUNs and single-threaded I/O submission. > On a related note, would not the current use of can_queue in SCSI lead to > poor resource utilization in MQ cases? Like, block layer allocating > nr_hw_queues * tags+request+driver_data.etc * can_queue, but SCSI limiting > the number of requests to can_queue. > Yes, indeed. That's another problem which we should be looking at. However, it's only ever relevant if we indeed implement some divvying logic; if we move to the shared tags approach it should work as designed. > BTW, if you would like me to try out this patch on my setup, please let me > know. > Oh, yes. Please do. Cheers, Hannes
On Thu, 6 Apr 2017, 1:49am, Hannes Reinecke wrote: > On 04/06/2017 08:27 AM, Arun Easi wrote: > > Hi Hannes, > > > > Thanks for taking a crack at the issue. My comments below.. > > > > On Tue, 4 Apr 2017, 5:07am, Hannes Reinecke wrote: > > > >> Most legacy HBAs have a tagset per HBA, not per queue. To map > >> these devices onto block-mq this patch implements a new tagset > >> flag BLK_MQ_F_GLOBAL_TAGS, which will cause the tag allocator > >> to use just one tagset for all hardware queues. > >> > >> Signed-off-by: Hannes Reinecke <hare@suse.com> > >> --- > >> block/blk-mq-tag.c | 12 ++++++++---- > >> block/blk-mq.c | 10 ++++++++-- > >> include/linux/blk-mq.h | 1 + > >> 3 files changed, 17 insertions(+), 6 deletions(-) > >> > >> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > >> index e48bc2c..a14e76c 100644 > >> --- a/block/blk-mq-tag.c > >> +++ b/block/blk-mq-tag.c > >> @@ -276,9 +276,11 @@ static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > >> void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, > >> busy_tag_iter_fn *fn, void *priv) > >> { > >> - int i; > >> + int i, lim = tagset->nr_hw_queues; > >> > >> - for (i = 0; i < tagset->nr_hw_queues; i++) { > >> + if (tagset->flags & BLK_MQ_F_GLOBAL_TAGS) > >> + lim = 1; > >> + for (i = 0; i < lim; i++) { > >> if (tagset->tags && tagset->tags[i]) > >> blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv); > >> } > >> @@ -287,12 +289,14 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, > >> > >> int blk_mq_reinit_tagset(struct blk_mq_tag_set *set) > >> { > >> - int i, j, ret = 0; > >> + int i, j, ret = 0, lim = set->nr_hw_queues; > >> > >> if (!set->ops->reinit_request) > >> goto out; > >> > >> - for (i = 0; i < set->nr_hw_queues; i++) { > >> + if (set->flags & BLK_MQ_F_GLOBAL_TAGS) > >> + lim = 1; > >> + for (i = 0; i < lim; i++) { > >> struct blk_mq_tags *tags = set->tags[i]; > >> > >> for (j = 0; j < tags->nr_tags; j++) { > >> diff --git a/block/blk-mq.c b/block/blk-mq.c > >> index 159187a..db96ed0 100644 > >> --- a/block/blk-mq.c > >> +++ b/block/blk-mq.c > >> @@ -2061,6 +2061,10 @@ static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx) > >> { > >> int ret = 0; > >> > >> + if ((set->flags & BLK_MQ_F_GLOBAL_TAGS) && hctx_idx != 0) { > >> + set->tags[hctx_idx] = set->tags[0]; > >> + return true; > >> + } > > : > > > BTW, if you would like me to try out this patch on my setup, please let me > > know. > > > Oh, yes. Please do. > Ran the tests on my setup (Dell R730, 2 Node). This change did not drop any IOPs (got ~2M 512b). The cache miss percentage was varying based on if the tests were running on one node or both (latter yperformed worse). All interrupts were directed to only 1 node. Interestingly, the cache miss percentage was lowest when MQ was off. I hit a fdisk hang (open path), btw, not sure if it has anything todo with this change, though. Notes and hang stack attached. Let me know if you are interested in any specific perf event/command-line. Regards, -Arun perf stat, ran on a short 10 second load. ---1port-1node-new-mq---- Performance counter stats for 'CPU(s) 2': 188,642,696 LLC-loads (66.66%) 3,615,142 LLC-load-misses # 1.92% of all LL-cache hits (66.67%) 86,488,341 LLC-stores (33.34%) 10,820,977 LLC-store-misses (33.33%) 391,370,104 cache-references (49.99%) 14,498,491 cache-misses # 3.705 % of all cache refs (66.66%) ---1port-1node-mq--- Performance counter stats for 'CPU(s) 2': 145,025,999 LLC-loads (66.67%) 3,793,427 LLC-load-misses # 2.62% of all LL-cache hits (66.67%) 60,878,939 LLC-stores (33.33%) 8,044,714 LLC-store-misses (33.33%) 294,713,070 cache-references (50.00%) 11,923,354 cache-misses # 4.046 % of all cache refs (66.66%) ---1port-1node-nomq--- Performance counter stats for 'CPU(s) 2': 157,375,709 LLC-loads (66.66%) 476,117 LLC-load-misses # 0.30% of all LL-cache hits (66.66%) 76,046,098 LLC-stores (33.34%) 840,756 LLC-store-misses (33.34%) 326,230,969 cache-references (50.00%) 1,332,398 cache-misses # 0.408 % of all cache refs (66.67%) ====================== --2port-allnodes-new-mq-- Performance counter stats for 'CPU(s) 2': 55,455,533 LLC-loads (66.67%) 37,996,545 LLC-load-misses # 68.52% of all LL-cache hits (66.67%) 14,030,291 LLC-stores (33.33%) 7,096,931 LLC-store-misses (33.33%) 76,711,197 cache-references (49.99%) 45,170,719 cache-misses # 58.884 % of all cache refs (66.66%) --2port-allnodes-mq-- Performance counter stats for 'CPU(s) 2': 59,303,410 LLC-loads (66.66%) 31,115,601 LLC-load-misses # 52.47% of all LL-cache hits (66.66%) 17,496,477 LLC-stores (33.34%) 6,201,373 LLC-store-misses (33.34%) 89,035,272 cache-references (50.00%) 37,372,777 cache-misses # 41.975 % of all cache refs (66.66%) --2port-allnodes-nomq-- Performance counter stats for 'CPU(s) 2': 86,724,905 LLC-loads (66.67%) 27,154,245 LLC-load-misses # 31.31% of all LL-cache hits (66.67%) 33,710,265 LLC-stores (33.34%) 6,521,394 LLC-store-misses (33.33%) 139,089,528 cache-references (50.00%) 33,682,000 cache-misses # 24.216 % of all cache refs (66.66%) Apr 6 17:34:05 avlnxperf kernel: INFO: task fdisk:27745 blocked for more than 120 seconds. Apr 6 17:34:05 avlnxperf kernel: Tainted: G B OE 4.11.0-rc4-newblk-ae+ #4 Apr 6 17:34:05 avlnxperf kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Apr 6 17:34:05 avlnxperf kernel: fdisk D 0 27745 27743 0x00000080 Apr 6 17:34:05 avlnxperf kernel: Call Trace: Apr 6 17:34:05 avlnxperf kernel: __schedule+0x289/0x8f0 Apr 6 17:34:05 avlnxperf kernel: schedule+0x36/0x80 Apr 6 17:34:05 avlnxperf kernel: schedule_timeout+0x249/0x300 Apr 6 17:34:05 avlnxperf kernel: ? sched_clock_cpu+0x11/0xb0 Apr 6 17:34:05 avlnxperf kernel: ? try_to_wake_up+0x59/0x450 Apr 6 17:34:05 avlnxperf kernel: wait_for_completion+0x121/0x180 Apr 6 17:34:05 avlnxperf kernel: ? wake_up_q+0x80/0x80 Apr 6 17:34:05 avlnxperf kernel: flush_work+0x11d/0x1c0 Apr 6 17:34:05 avlnxperf kernel: ? wake_up_worker+0x30/0x30 Apr 6 17:34:05 avlnxperf kernel: __cancel_work_timer+0x10e/0x1d0 Apr 6 17:34:05 avlnxperf kernel: ? kobj_lookup+0x10d/0x160 Apr 6 17:34:05 avlnxperf kernel: cancel_delayed_work_sync+0x13/0x20 Apr 6 17:34:05 avlnxperf kernel: disk_block_events+0x77/0x80 Apr 6 17:34:05 avlnxperf kernel: __blkdev_get+0x11b/0x4b0 Apr 6 17:34:05 avlnxperf kernel: blkdev_get+0x1c3/0x320 Apr 6 17:34:05 avlnxperf kernel: blkdev_open+0x5b/0x70 Apr 6 17:34:05 avlnxperf kernel: do_dentry_open+0x213/0x330 Apr 6 17:34:05 avlnxperf kernel: ? bd_acquire+0xd0/0xd0 Apr 6 17:34:05 avlnxperf kernel: vfs_open+0x4f/0x70 Apr 6 17:34:05 avlnxperf kernel: ? may_open+0x9b/0x100 Apr 6 17:34:05 avlnxperf kernel: path_openat+0x557/0x13c0 Apr 6 17:34:05 avlnxperf kernel: ? generic_file_read_iter+0x746/0x8c0 Apr 6 17:34:05 avlnxperf kernel: ? scsi_bios_ptable+0x54/0x130 Apr 6 17:34:05 avlnxperf kernel: do_filp_open+0x91/0x100 Apr 6 17:34:05 avlnxperf kernel: ? __alloc_fd+0x46/0x170 Apr 6 17:34:05 avlnxperf kernel: do_sys_open+0x124/0x210 Apr 6 17:34:05 avlnxperf kernel: ? __audit_syscall_exit+0x209/0x290 Apr 6 17:34:05 avlnxperf kernel: SyS_open+0x1e/0x20 Apr 6 17:34:05 avlnxperf kernel: do_syscall_64+0x67/0x180 Apr 6 17:34:05 avlnxperf kernel: entry_SYSCALL64_slow_path+0x25/0x25 Apr 6 17:34:05 avlnxperf kernel: RIP: 0033:0x7faef86b0a10 Apr 6 17:34:05 avlnxperf kernel: RSP: 002b:00007fffa7159438 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 Apr 6 17:34:05 avlnxperf kernel: RAX: ffffffffffffffda RBX: 0000000000b34310 RCX: 00007faef86b0a10 Apr 6 17:34:05 avlnxperf kernel: RDX: 00007fffa7159598 RSI: 0000000000080000 RDI: 00007fffa7159590 Apr 6 17:34:05 avlnxperf kernel: RBP: 00007fffa7159590 R08: 00007faef8610938 R09: 0000000000000008 Apr 6 17:34:05 avlnxperf kernel: R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000 Apr 6 17:34:05 avlnxperf kernel: R13: 0000000000b34550 R14: 0000000000000005 R15: 0000000000000000
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index e48bc2c..a14e76c 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -276,9 +276,11 @@ static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, busy_tag_iter_fn *fn, void *priv) { - int i; + int i, lim = tagset->nr_hw_queues; - for (i = 0; i < tagset->nr_hw_queues; i++) { + if (tagset->flags & BLK_MQ_F_GLOBAL_TAGS) + lim = 1; + for (i = 0; i < lim; i++) { if (tagset->tags && tagset->tags[i]) blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv); } @@ -287,12 +289,14 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, int blk_mq_reinit_tagset(struct blk_mq_tag_set *set) { - int i, j, ret = 0; + int i, j, ret = 0, lim = set->nr_hw_queues; if (!set->ops->reinit_request) goto out; - for (i = 0; i < set->nr_hw_queues; i++) { + if (set->flags & BLK_MQ_F_GLOBAL_TAGS) + lim = 1; + for (i = 0; i < lim; i++) { struct blk_mq_tags *tags = set->tags[i]; for (j = 0; j < tags->nr_tags; j++) { diff --git a/block/blk-mq.c b/block/blk-mq.c index 159187a..db96ed0 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2061,6 +2061,10 @@ static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx) { int ret = 0; + if ((set->flags & BLK_MQ_F_GLOBAL_TAGS) && hctx_idx != 0) { + set->tags[hctx_idx] = set->tags[0]; + return true; + } set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx, set->queue_depth, set->reserved_tags); if (!set->tags[hctx_idx]) @@ -2080,8 +2084,10 @@ static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set, unsigned int hctx_idx) { if (set->tags[hctx_idx]) { - blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx); - blk_mq_free_rq_map(set->tags[hctx_idx]); + if (!(set->flags & BLK_MQ_F_GLOBAL_TAGS) || hctx_idx == 0) { + blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx); + blk_mq_free_rq_map(set->tags[hctx_idx]); + } set->tags[hctx_idx] = NULL; } } diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index b296a90..eee27b016 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -155,6 +155,7 @@ enum { BLK_MQ_F_DEFER_ISSUE = 1 << 4, BLK_MQ_F_BLOCKING = 1 << 5, BLK_MQ_F_NO_SCHED = 1 << 6, + BLK_MQ_F_GLOBAL_TAGS = 1 << 7, BLK_MQ_F_ALLOC_POLICY_START_BIT = 8, BLK_MQ_F_ALLOC_POLICY_BITS = 1,
Most legacy HBAs have a tagset per HBA, not per queue. To map these devices onto block-mq this patch implements a new tagset flag BLK_MQ_F_GLOBAL_TAGS, which will cause the tag allocator to use just one tagset for all hardware queues. Signed-off-by: Hannes Reinecke <hare@suse.com> --- block/blk-mq-tag.c | 12 ++++++++---- block/blk-mq.c | 10 ++++++++-- include/linux/blk-mq.h | 1 + 3 files changed, 17 insertions(+), 6 deletions(-)