From: Jens Axboe <axboe@fb.com>
To: Dan Williams <dan.j.williams@intel.com>, linux-ide@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>, Shaohua Li <shli@fb.com>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 2/2] libata: micro-optimize tag allocation
Date: Fri, 16 Jan 2015 16:17:21 -0700 [thread overview]
Message-ID: <54B99C01.2030507@fb.com> (raw)
In-Reply-To: <20150116231307.18771.52330.stgit@viggo.jf.intel.com>
On 01/16/2015 04:13 PM, Dan Williams wrote:
> Jens notes, "libata tag allocator sucks. Like seriously sucks, it's
> almost a worst case implementation." Previously I thought SATA mmio
> latency dominated performance profiles, but as Tejun notes:
>
> "Hmmm... one problem with the existing tag allocator in ata is that
> it's not very efficient which actually shows up in profile when libata
> is used with a very zippy SSD. Given that ata needs a different
> allocation policies anyway maybe the right thing to do is making the
> existing allocator suck less."
>
> So replace it with a naive enhancement that also supports the existing
> quirks. Hopefully, soon to be replaced by Shaohua's patches [1], but
> those do not yet support the quirk needed by sil24 (ATA_FLAG_LOWTAG)
> [2].
That's trivial to do, it's just always having '0' in the cache and
that's where the search would start.
--
Jens Axboe
next prev parent reply other threads:[~2015-01-16 23:17 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-16 23:12 [PATCH 0/2] fix sil24 regression and muddy the ata tag allocation waters Dan Williams
2015-01-16 23:13 ` [PATCH 1/2] libata: allow sata_sil24 to opt-out of tag ordered submission Dan Williams
2015-01-17 10:59 ` Sergei Shtylyov
[not found] ` <CAPcyv4h3n+cnvADiEbGgi1EFCqEwhzZ7gt_6XUmSC62aOf2Dzw@mail.gmail.com>
2015-01-17 18:43 ` Sergei Shtylyov
2015-01-19 14:12 ` Tejun Heo
2015-01-19 14:24 ` Sergei Shtylyov
2015-01-19 14:27 ` Tejun Heo
2015-01-19 14:13 ` Tejun Heo
2015-01-16 23:13 ` [PATCH 2/2] libata: micro-optimize tag allocation Dan Williams
2015-01-16 23:17 ` Jens Axboe [this message]
2015-01-16 23:19 ` Dan Williams
2015-01-16 23:21 ` Jens Axboe
2015-01-16 23:38 ` Dan Williams
2015-01-16 23:31 ` Shaohua Li
2015-01-16 23:49 ` Dan Williams
2015-01-16 23:55 ` Shaohua Li
2015-01-16 23:59 ` Dan Williams
2015-01-17 0:10 ` Shaohua Li
2015-01-19 14:14 ` Tejun Heo
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