From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
Jeff Moyer <jmoyer@redhat.com>, Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH V2 2/4] blk-mq: fix shared queue mapping
Date: Mon, 17 Dec 2018 11:57:25 +0100 [thread overview]
Message-ID: <20181217105725.GA5826@lst.de> (raw)
In-Reply-To: <20181217104248.5828-3-ming.lei@redhat.com>
On Mon, Dec 17, 2018 at 06:42:46PM +0800, Ming Lei wrote:
> From: Christoph Hellwig <hch@lst.de>
>
> Even though poll_queues are zero, nvme's mapping for HCTX_TYPE_POLL still
> may be setup via blk_mq_map_queues() which cause different mapping compared
> with HCTX_TYPE_DEFAULT's mapping built from managed irq affinity.
>
> This mapping will cause hctx->type to be over-written in blk_mq_map_swqueue(),
> then the whole mapping may become broken, for example, one same ctx can be
> mapped to different hctxs with same hctx type. This bad mapping has caused
> IO hang in simple dd test, as reported by Mike.
>
> This patch sets map->nr_queues as zero explictly if there is zero
> queues for such queue type, also maps to correct hctx if .nr_queues of the
> queue type is zero.
>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Mike Snitzer <snitzer@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
>
> (don't handle zero .nr_queues map in blk_mq_map_swqueue())
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
I actually think we should split this into three patches:
1) skip zero-queue maps in blk_mq_map_swqueue
2) skip zero-queue maps in blk_mq_map_queue
3) don't duplicate maps in nvme
sorry for misleading you with my quick WIP patch.
I can send send patches for my two with a proper changelogs, but
I'll leave blk_mq_map_swqueue to you as I don't full understand
the rationale, even if it looks sensible to me.
next prev parent reply other threads:[~2018-12-17 10:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-17 10:42 [PATCH V2 0/4] blk-mq: queue mapping fix & improvement Ming Lei
2018-12-17 10:42 ` [PATCH V2 1/4] blk-mq: fix allocation for queue mapping table Ming Lei
2018-12-17 10:42 ` [PATCH V2 2/4] blk-mq: fix shared queue mapping Ming Lei
2018-12-17 10:57 ` Christoph Hellwig [this message]
2018-12-17 11:06 ` Ming Lei
2018-12-17 10:42 ` [PATCH V2 3/4] blk-mq: fix dispatch from sw queue Ming Lei
2018-12-17 11:08 ` Christoph Hellwig
2018-12-17 11:15 ` Ming Lei
2018-12-17 11:16 ` Christoph Hellwig
2018-12-17 10:42 ` [PATCH V2 4/4] blk-mq: export hctx->type in debugfs instead of sysfs Ming Lei
2018-12-17 10:57 ` Christoph Hellwig
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