From: Ming Lei <ming.lei@redhat.com>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Bart Van Assche <bvanassche@acm.org>,
Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
"Martin K . Petersen" <martin.petersen@oracle.com>,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-scsi@vger.kernel.org, Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCH 1/5] blk-mq: move srcu from blk_mq_hw_ctx to request_queue
Date: Mon, 22 Nov 2021 21:08:38 +0800 [thread overview]
Message-ID: <YZuWVlakjrzICKc1@T590> (raw)
In-Reply-To: <a219fff8-8f2d-adb1-eb8c-3e5712cea5bd@grimberg.me>
On Mon, Nov 22, 2021 at 09:48:35AM +0200, Sagi Grimberg wrote:
>
> > > > + bool alloc_srcu;
> > >
> > > I found the following statement multiple times in this patch:
> > >
> > > WARN_ON_ONCE(q->alloc_srcu != !!(q->tag_set->flags & BLK_MQ_F_BLOCKING));
> > >
> > > Does this mean that the new q->alloc_srcu member variable can be left out
> > > and that it can be replaced with the following test?
> > >
> > > q->tag_set->flags & BLK_MQ_F_BLOCKING
> >
> > q->tag_set can't be used anymore after blk_cleanup_queue() returns,
> > and we need the flag for freeing request_queue instance.
>
> Why not just look at the queue->srcu pointer? it is allocated only
> for BLK_MQ_F_BLOCKING no?
Yeah, we can add one extra srcu pointer to request queue, but this way
needs one extra fetch to q->srcu in fast path compared with current
code base, so io_uring workload may be affected a bit.
Thanks,
Ming
next prev parent reply other threads:[~2021-11-22 13:08 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-19 2:18 [PATCH 0/5] blk-mq: quiesce improvement Ming Lei
2021-11-19 2:18 ` [PATCH 1/5] blk-mq: move srcu from blk_mq_hw_ctx to request_queue Ming Lei
2021-11-19 4:30 ` Bart Van Assche
2021-11-19 8:10 ` Ming Lei
2021-11-22 7:48 ` Sagi Grimberg
2021-11-22 13:08 ` Ming Lei [this message]
2021-11-22 13:47 ` Sagi Grimberg
2021-11-19 2:18 ` [PATCH 2/5] blk-mq: rename hctx_lock & hctx_unlock Ming Lei
2021-11-22 7:53 ` Sagi Grimberg
2021-11-22 13:20 ` Ming Lei
2021-11-22 13:50 ` Sagi Grimberg
2021-11-23 0:08 ` Ming Lei
2021-11-23 8:54 ` Sagi Grimberg
2021-11-22 9:00 ` Christoph Hellwig
2021-11-19 2:18 ` [PATCH 3/5] blk-mq: add helper of blk_mq_global_quiesce_wait() Ming Lei
2021-11-22 7:56 ` Sagi Grimberg
2021-11-22 8:00 ` Sagi Grimberg
2021-11-22 13:26 ` Ming Lei
2021-11-22 13:55 ` Sagi Grimberg
2021-11-23 0:17 ` Ming Lei
2021-11-23 9:00 ` Sagi Grimberg
2021-11-30 2:33 ` Ming Lei
2021-12-08 12:49 ` Sagi Grimberg
2021-12-10 2:02 ` Ming Lei
2021-11-19 2:18 ` [PATCH 4/5] nvme: quiesce namespace queue in parallel Ming Lei
2021-11-22 8:07 ` Sagi Grimberg
2021-11-23 0:13 ` Ming Lei
2021-11-19 2:18 ` [PATCH 5/5] scsi: use blk-mq quiesce APIs to implement scsi_host_block Ming Lei
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