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From: Alexander Gordeev <agordeev@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Kent Overstreet <kmo@daterainc.com>, Jens Axboe <axboe@kernel.dk>,
	Shaohua Li <shli@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [patch 1/2]percpu_ida: fix a live lock
Date: Mon, 10 Feb 2014 16:49:17 +0100	[thread overview]
Message-ID: <20140210154917.GC320@dhcp-26-207.brq.redhat.com> (raw)
In-Reply-To: <20140210122942.GB320@dhcp-26-207.brq.redhat.com>

On Mon, Feb 10, 2014 at 01:29:42PM +0100, Alexander Gordeev wrote:
> > We'll defintively need a fix to be able to allow the whole tag space.
> > For large numbers of tags per device the flush might work, but for
> > devices with low number of tags we need something more efficient.  The
> > case of less tags than CPUs isn't that unusual either and we probably
> > want to switch to an allocator without per cpu allocations for them to
> > avoid all this.  E.g. for many ATA devices we just have a single tag,
> > and many scsi drivers also only want single digit outstanding commands
> > per LUN.
> 
> Do we really always need the pool for these classes of devices?
> 
> Pulling tags from local caches to the pool just to (near to) dry it at
> the very next iteration does not seem beneficial. Not to mention caches
> vs pool locking complexities.

And I meant here we do not scrap per cpu allocations.

-- 
Regards,
Alexander Gordeev
agordeev@redhat.com

  reply	other threads:[~2014-02-10 15:47 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-31  3:38 [patch 1/2]percpu_ida: fix a live lock Shaohua Li
2014-01-04 21:08 ` Kent Overstreet
2014-01-05 13:13   ` Shaohua Li
2014-01-06 20:46     ` Kent Overstreet
2014-01-06 20:52       ` Jens Axboe
2014-01-06 21:47         ` Kent Overstreet
2014-02-09 15:50           ` Alexander Gordeev
2014-02-10 10:32             ` Christoph Hellwig
2014-02-10 12:29               ` Alexander Gordeev
2014-02-10 15:49                 ` Alexander Gordeev [this message]
2014-02-10 16:16                   ` Christoph Hellwig
2014-02-10 16:26               ` Jens Axboe
2014-02-10 22:41                 ` Kent Overstreet
2014-02-10 23:06                   ` Jens Axboe
2014-02-11  9:12                     ` Christoph Hellwig
2014-02-11 14:42                       ` James Bottomley
2014-02-11 14:53                         ` Christoph Hellwig
2014-02-14 10:36                     ` Alexander Gordeev

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