From: Christoph Hellwig <hch@infradead.org>
To: Shlomo Pongratz <shlomop@mellanox.com>
Cc: axboe@kernel.dk, linux-scsi@vger.kernel.org
Subject: Re: [PATCH] block/null_blk: Fix completion processing from LIFO to FIFO
Date: Thu, 6 Feb 2014 08:35:42 -0800 [thread overview]
Message-ID: <20140206163542.GA30008@infradead.org> (raw)
In-Reply-To: <1391704397-26816-1-git-send-email-shlomop@mellanox.com>
On Thu, Feb 06, 2014 at 06:33:17PM +0200, Shlomo Pongratz wrote:
> The completion queue is implemented using lockless list.
>
> The llist_add is adds the events to the list head which is a push operation.
> The processing of the completion elements is done by disconnecting all the
> pushed elements and iterating over the disconnected list. The problem is
> that the processing is done in reverse order w.r.t order of the insertion
> i.e. LIFO processing. By reversing the disconnected list which is done in
> linear time the desired FIFO processing is achieved.
I think it should just switch to using __smp_call_function_single
directly, mirroring commit 3d6efbf62c797a2924785f482e4ce8aa8820ec72 for
the blk-mq core.
I've actually a patch in the queue that allows generic request
completion offloading similar to blk_complete_request() in the old
request code, but it'll need a bit more polishing first.
next prev parent reply other threads:[~2014-02-06 16:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-06 16:33 [PATCH] block/null_blk: Fix completion processing from LIFO to FIFO Shlomo Pongratz
2014-02-06 16:35 ` Christoph Hellwig [this message]
2014-02-06 19:23 ` Jens Axboe
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