linux-kernel - Re: [PATCH v2 0/3] block: avoid hctx spinlock for plug with multiple queues

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Message-Id: <174619952950.748556.3719586120129055173.b4-ty@kernel.dk>
Date: Fri, 02 May 2025 09:25:29 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Caleb Sander Mateos <csander@...estorage.com>
Cc: Christoph Hellwig <hch@...radead.org>, linux-block@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] block: avoid hctx spinlock for plug with
 multiple queues


On Fri, 25 Apr 2025 19:17:25 -0600, Caleb Sander Mateos wrote:
> blk_mq_flush_plug_list() has a fast path if all requests in the plug
> are destined for the same request_queue. It calls ->queue_rqs() with the
> whole batch of requests, falling back on ->queue_rq() for any requests
> not handled by ->queue_rqs(). However, if the requests are destined for
> multiple queues, blk_mq_flush_plug_list() has a slow path that calls
> blk_mq_dispatch_list() repeatedly to filter the requests by ctx/hctx.
> Each queue's requests are inserted into the hctx's dispatch list under a
> spinlock, then __blk_mq_sched_dispatch_requests() takes them out of the
> dispatch list (taking the spinlock again), and finally
> blk_mq_dispatch_rq_list() calls ->queue_rq() on each request.
> 
> [...]

Applied, thanks!

[1/3] block: take rq_list instead of plug in dispatch functions
      commit: 0aeb7ebfc7e3d4bef3542aadd33505452d2f9b82
[2/3] block: factor out blk_mq_dispatch_queue_requests() helper
      commit: a5728a1d1ef2d927c67e73fda94946c2c15106df
[3/3] block: avoid hctx spinlock for plug with multiple queues
      commit: 9712c57ec1117d6b5fe1cc8ad420049171140b26

Best regards,
-- 
Jens Axboe