From: Gionatan Danti <g.danti@assyoma.it>
To: linux-kernel@vger.kernel.org
Cc: g.danti@assyoma.it
Subject: Re: AHCI maximum transfer size
Date: Wed, 12 Nov 2014 10:54:32 +0100 [thread overview]
Message-ID: <54632E58.60709@assyoma.it> (raw)
In-Reply-To: <5417FB30.8030908@assyoma.it>
On 16/09/2014 10:56, Gionatan Danti wrote:
>> Hi all,
>> I searched the list and the internet for this question, but I did not
>> find a definitive answer.
>>
>> I wonder what is the maximum AHCI transfer size for kernel 2.6.32.x
>> Let me explain: using a command as "dd if=/dev/zero of=/dev/sda bs=2M" I
>> can see, via iostat, that request-size is at 2M (as expected). However
>> it seems to me that the effective transfer size is way lower: disabling
>> writeback cache on the target disk, I see very low performance even for
>> big-chunk transfers.
>>
>> Googling, I found this post on stackoverflow stating that maximum
>> observerd AHCI transfer size (with a SATA protocol analyzer) is 128KB:
>> http://stackoverflow.com/questions/24053662/how-to-enlarge-sata-transfer-size-in-linux-ahci-driver.
>>
>>
>> The stackoverflow post seems to agree with this old LWN.net article:
>> http://lwn.net/Articles/77981/
>>
>> Anyone has any idea of how to find (and eventually change) the used AHCI
>> transfer size without touching the code?
>>
>> NOTE: please CC me directly.
>> Regards.
>>
>
> Hi all,
> any idea on the subject?
>
> Regards.
Hi guys,
anyone with a suggestion?
Thank you.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8
prev parent reply other threads:[~2014-11-12 10:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-11 14:32 AHCI maximum transfer size Gionatan Danti
2014-09-16 8:56 ` Gionatan Danti
2014-11-12 9:54 ` Gionatan Danti [this message]
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