From: Tejun Heo <tj@kernel.org>
To: Marc C <marc.ceeeee@gmail.com>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
Alexander Gordeev <agordeev@redhat.com>,
Jens Axboe <axboe@kernel.dk>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Mike Christie <michaelc@cs.wisc.edu>,
linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org,
Jeff Garzik <jgarzik@pobox.com>,
linux-scsi <linux-scsi@vger.kernel.org>
Subject: Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing
Date: Wed, 31 Jul 2013 06:23:03 -0400 [thread overview]
Message-ID: <20130731102303.GC2810@htj.dyndns.org> (raw)
In-Reply-To: <CAO1A-8AW-aQJ0hjX38U_q8Ovcpb58fP9Skfyi59xihXTQHECNQ@mail.gmail.com>
Hello,
On Tue, Jul 30, 2013 at 09:16:02PM -0700, Marc C wrote:
> >> One thing which would probably be worthwhile tho is getting rid of the
> >> bitmap based qc tag allocator in libata. That one is just borderline
> >> stupid to keep around on any setup which is supposed to be scalable.
> > Your border might be wider than mine :-). Yes, the bitmap should
> > definitely go.
>
> A naive implementation is obviously less-than-efficient. However, what
> other problems exist with the libata QC tag allocator? I highly doubt
> SATA will change to beyond 32 queue tags, primarily because it would
> be a pain to change SDB FIS (it's likely to break the dozens of AHCI
> controller implementations out there). Further, it seems like the
> industry stopped caring about SATA and is pushing NVMe for future
> offerings.
>
> In any event, most modern systems should have instructions to count
> leading zeroes and modify bits atomically.
It's inefficient not because scanning is expensive but because it
makes all CPUs in the system to hit on the exact same cacheline over
and over and over again.
Thanks.
--
tejun
next prev parent reply other threads:[~2013-07-31 10:23 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-21 19:00 [PATCH RESEND 0/1] AHCI: Optimize interrupt processing Alexander Gordeev
2013-05-21 19:00 ` [PATCH RESEND 1/1] " Alexander Gordeev
2013-05-21 23:50 ` [PATCH RESEND 0/1] " Tejun Heo
2013-05-22 14:39 ` Alexander Gordeev
2013-05-22 17:03 ` Jens Axboe
2013-07-11 10:26 ` Alexander Gordeev
2013-07-11 23:00 ` Nicholas A. Bellinger
2013-07-12 7:46 ` Alexander Gordeev
2013-07-13 5:20 ` Nicholas A. Bellinger
2013-07-16 18:32 ` Alexander Gordeev
2013-07-16 21:38 ` Nicholas A. Bellinger
2013-07-17 16:19 ` Alexander Gordeev
2013-07-18 18:51 ` Nicholas A. Bellinger
2013-07-18 19:12 ` Mike Christie
2013-07-19 0:23 ` Nicholas A. Bellinger
2013-07-19 0:30 ` Jens Axboe
2013-07-19 1:03 ` Nicholas A. Bellinger
2013-07-19 6:34 ` Nicholas A. Bellinger
2013-07-19 15:33 ` James Bottomley
2013-07-19 21:01 ` Nicholas A. Bellinger
2013-07-20 4:56 ` Nicholas A. Bellinger
2013-07-20 14:48 ` Mike Christie
2013-07-20 22:14 ` Nicholas A. Bellinger
2013-07-20 23:57 ` Jens Axboe
2013-08-09 19:15 ` Alexander Gordeev
2013-08-09 20:17 ` Nicholas A. Bellinger
2013-08-15 16:23 ` Alexander Gordeev
2013-08-16 2:19 ` Nicholas A. Bellinger
2013-08-16 16:41 ` Alexander Gordeev
2013-08-16 17:46 ` Nicholas A. Bellinger
2013-08-28 15:56 ` Alexander Gordeev
2013-09-20 15:19 ` Alexander Gordeev
2013-09-20 20:41 ` Nicholas A. Bellinger
2013-10-03 11:06 ` Christoph Hellwig
2013-10-07 14:44 ` Alexander Gordeev
2013-07-22 15:03 ` Alexander Gordeev
2013-07-22 21:10 ` Nicholas A. Bellinger
2013-07-25 10:16 ` Alexander Gordeev
2013-07-25 22:08 ` Nicholas A. Bellinger
2013-07-26 2:09 ` Jens Axboe
2013-07-26 21:14 ` Nicholas A. Bellinger
2013-07-27 0:43 ` Nicholas A. Bellinger
2013-07-29 11:18 ` Alexander Gordeev
2013-07-29 14:08 ` Jens Axboe
2013-07-29 19:19 ` Nicholas A. Bellinger
2013-07-31 4:16 ` Marc C
2013-07-31 10:23 ` Tejun Heo [this message]
2013-07-29 11:50 ` Tejun Heo
2013-07-29 19:11 ` Nicholas A. Bellinger
2013-07-29 11:46 ` Tejun Heo
2013-07-29 14:03 ` Jens Axboe
2013-08-09 8:23 ` Alexander Gordeev
2013-08-09 14:15 ` Tejun Heo
2013-08-09 14:24 ` Jens Axboe
2013-08-09 15:07 ` Alexander Gordeev
2013-08-09 15:52 ` Jens Axboe
2013-08-09 16:46 ` Alexander Gordeev
2013-08-09 17:07 ` Jens Axboe
2013-08-12 15:21 ` Alexander Gordeev
2013-07-29 7:28 ` Hannes Reinecke
2013-07-31 17:11 ` Alexander Gordeev
2013-07-19 15:58 ` Mike Christie
2013-07-19 21:05 ` Nicholas A. Bellinger
2013-07-18 19:14 ` Nicholas A. Bellinger
2013-07-18 21:21 ` Jens Axboe
2014-09-11 12:42 ` Alexander Gordeev
2014-09-11 12:44 ` [PATCH v2] " Alexander Gordeev
2014-09-13 4:43 ` Tejun Heo
2014-09-11 13:36 ` [PATCH RESEND 0/1] " Bartlomiej Zolnierkiewicz
2014-09-13 4:46 ` Tejun Heo
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