linux-kernel - Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish

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Message-ID: <CA+55aFza9mK0=auaRijA397tHZp+kghczYrS9L6j1O6UTnGJyA@mail.gmail.com>
Date:	Fri, 11 Sep 2015 16:13:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chris Mason <clm@...com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josef Bacik <jbacik@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>,
	Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish_plug()

On Fri, Sep 11, 2015 at 4:06 PM, Chris Mason <clm@...com> wrote:
>
> Originally I was worried about the latency impact of holding the
> plugs over more than one super with high end flash.  I just didn't want
> to hold onto the IO for longer than we had to.
>
> But, since this isn't really latency sensitive anyway, if we find we're
> not keeping the flash pipelines full the right answer is to short
> circuit the plugging in general.  I'd agree actual throughput should be
> the same.

Yeah, this only triggers for system-wide writeback, so I don't seer
that it should be latency-sensitive at that level, afaik.

But hey, it's IO, and I've been surprised by magic pattern
sensitivites before...

                  Linus
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