From: John Garry <firstname.lastname@example.org> To: Ming Lei <email@example.com> Cc: Jens Axboe <firstname.lastname@example.org>, <email@example.com>, "Bart Van Assche" <firstname.lastname@example.org>, Hannes Reinecke <email@example.com>, "Christoph Hellwig" <firstname.lastname@example.org>, Thomas Gleixner <email@example.com>, Keith Busch <firstname.lastname@example.org> Subject: Re: [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug Date: Mon, 21 Oct 2019 10:47:05 +0100 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <20191021093448.GA22635@ming.t460p> On 21/10/2019 10:34, Ming Lei wrote: > On Mon, Oct 21, 2019 at 10:19:18AM +0100, John Garry wrote: >> On 20/10/2019 11:14, Ming Lei wrote: >>>>> ght? If so, I need to find some simple sysfs entry to >>>>>>> tell me of this occurrence, to trigger the capture. Or add something. My >>>>>>> script is pretty dump. >>>>>>> >>>>>>> BTW, I did notice that we the dump_stack in __blk_mq_run_hw_queue() >>>>>>> pretty soon before the problem happens - maybe a clue or maybe coincidence. >>>>>>> >>>>> >>>>> I finally got to capture that debugfs dump at the point the SCSI IOs >>>>> timeout, as attached. Let me know if any problem receiving it. >>>>> >>>>> Here's a kernel log snippet at that point (I added some print for the >>>>> timeout): >>>>> >>>>> 609] psci: CPU6 killed. >>>>> [ 547.722217] CPU5: shutdown >>>>> [ 547.724926] psci: CPU5 killed. >>>>> [ 547.749951] irq_shutdown >>>>> [ 547.752701] IRQ 800: no longer affine to CPU4 >>>>> [ 547.757265] CPU4: shutdown >>>>> [ 547.759971] psci: CPU4 killed. >>>>> [ 547.790348] CPU3: shutdown >>>>> [ 547.793052] psci: CPU3 killed. >>>>> [ 547.818330] CPU2: shutdown >>>>> [ 547.821033] psci: CPU2 killed. >>>>> [ 547.854285] CPU1: shutdown >>>>> [ 547.856989] psci: CPU1 killed. >>>>> [ 575.925307] scsi_timeout req=0xffff0023b0dd9c00 reserved=0 >>>>> [ 575.930794] scsi_timeout req=0xffff0023b0df2700 reserved=0 >>>> From the debugfs log, 66 requests are dumped, and 63 of them has >>> been submitted to device, and the other 3 is in ->dispatch list >>> via requeue after timeout is handled. >>> >> >> Hi Ming, >> >>> You mentioned that: >>> >>> " - I added some debug prints in blk_mq_hctx_drain_inflight_rqs() for when >>> inflights rqs !=0, and I don't see them for this timeout" >>> >>> There might be two reasons: >>> >>> 1) You are still testing a multiple reply-queue device? >> >> As before, I am testing by exposing mutliple queues to the SCSI midlayer. I >> had to make this change locally, as on mainline we still only expose a >> single queue and use the internal reply queue when enabling managed >> interrupts. >> >> As I >>> mentioned last times, it is hard to map reply-queue into blk-mq >>> hctx correctly. >> >> Here's my branch, if you want to check: >> >> https://github.com/hisilicon/kernel-dev/commits/private-topic-sas-5.4-mq-v4 >> >> It's a bit messy (sorry), but you can see that the reply-queue in the LLDD >> is removed in commit 087b95af374. >> >> I am now thinking of actually making this change to the LLDD in mainline to >> avoid any doubt in future. > > As I mentioned last time, you do share tags among all MQ queues on your hardware > given your hardware is actually SQ HBA, so commit 087b95af374 is definitely > wrong, isn't it? > Yes, we share tags among all queues, but we generate the tag - known as IPTT - in the LLDD now, as we can no longer use the request tag (as it is not unique per all queues): https://github.com/hisilicon/kernel-dev/commit/087b95af374be6965583c1673032fb33bc8127e8#diff-f5d8fff19bc539a7387af5230d4e5771R188 As I said, the branch is messy and I did have to fix 087b95af374. > It can be very hard to partition the single tags among multiple hctx. > I really do think now that I'll make this change on mainline to avoid doubt... Thanks, John > > Thanks, > Ming > > > . >
next prev parent reply other threads:[~2019-10-21 9:47 UTC|newest] Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-14 1:50 Ming Lei 2019-10-14 1:50 ` [PATCH V4 1/5] blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED Ming Lei 2019-10-14 1:50 ` [PATCH V4 2/5] blk-mq: prepare for draining IO when hctx's all CPUs are offline Ming Lei 2019-10-14 1:50 ` [PATCH V4 3/5] blk-mq: stop to handle IO and drain IO before hctx becomes dead Ming Lei 2019-11-28 9:29 ` John Garry 2019-10-14 1:50 ` [PATCH V4 4/5] blk-mq: re-submit IO in case that hctx is dead Ming Lei 2019-10-14 1:50 ` [PATCH V4 5/5] blk-mq: handle requests dispatched from IO scheduler " Ming Lei 2019-10-16 8:58 ` [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug John Garry 2019-10-16 12:07 ` Ming Lei 2019-10-16 16:19 ` John Garry [not found] ` <firstname.lastname@example.org> 2019-10-20 10:14 ` Ming Lei 2019-10-21 9:19 ` John Garry 2019-10-21 9:34 ` Ming Lei 2019-10-21 9:47 ` John Garry [this message] 2019-10-21 10:24 ` Ming Lei 2019-10-21 11:49 ` John Garry 2019-10-21 12:53 ` Ming Lei 2019-10-21 14:02 ` John Garry 2019-10-22 0:16 ` Ming Lei 2019-10-22 11:19 ` John Garry 2019-10-22 13:45 ` Ming Lei 2019-10-25 16:33 ` John Garry 2019-10-28 10:42 ` Ming Lei 2019-10-28 11:55 ` John Garry 2019-10-29 1:50 ` Ming Lei 2019-10-29 9:22 ` John Garry 2019-10-29 10:05 ` Ming Lei 2019-10-29 17:54 ` John Garry 2019-10-31 16:28 ` John Garry 2019-11-28 1:09 ` chenxiang (M) 2019-11-28 2:02 ` Ming Lei 2019-11-28 10:45 ` John Garry
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