linux-kernel - Re: [Scst-devel] Fwd: Re: linuxcon 2010...

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Message-ID: <20100824072557.GK2804@reaktio.net>
Date:	Tue, 24 Aug 2010 10:25:57 +0300
From:	Pasi Kärkkäinen <pasik@....fi>
To:	Chetan Loke <chetanloke@...il.com>
Cc:	Bart Van Assche <bvanassche@....org>,
	Vladislav Bolkhovitin <vst@...b.net>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	James Bottomley <James.Bottomley@...e.de>,
	scst-devel <scst-devel@...ts.sourceforge.net>
Subject: Re: [Scst-devel] Fwd: Re: linuxcon 2010...

On Mon, Aug 23, 2010 at 02:03:26PM -0400, Chetan Loke wrote:
> I actually received 3+ off-post emails asking whether I was talking
> about initiator or target in the 100K IOPS case below and what did I
> mean by the ACKs.
> I was referring to the 'Initiator' side.
> ACKs == When scsi-ML down-calls the LLD via the queue-command, process
> the sgl's(if you like) and then trigger the scsi_done up-call path.
> 

Uhm, Intel and Microsoft demonstrated over 1 million IOPS
using software iSCSI and a single 10 Gbit Ethernet NIC (Intel 82599).

How come there is such a huge difference? What are we lacking in Linux? 

-- Pasi

> Chetan Loke
> 
> On Mon, Aug 23, 2010 at 12:07 PM, Chetan Loke <chetanloke@...il.com> wrote:
> > On Mon, Aug 23, 2010 at 11:11 AM, Bart Van Assche <bvanassche@....org> wrote:
> >
> >>
> >> There is an important design difference between SCST and LIO: SCST by
> >> defaults creates multiple threads to process the I/O operations for a
> >> storage target, while LIO only creates a single thread per storage target.
> >> This makes SCST perform measurably faster.
> >>
> >
> > Forget that. You could have discussed this if there were code reviews
> > or other mainline inclusion emails from James B. From what I have
> > heard, the decision was taken around 8-9 months back.
> > Would anyone like to either comment/validate/refute this please?  If
> > not then I would kindly request these guys to stop taking us for a
> > test drive. And also I'm not sure when was the last time James B.
> > bench-marked our scsi-stack. Even if I ACK in the xmit-path then I
> > can't push more than 100K IOPs. But other folks have re-engineered our
> > linux-scsi stack and from what I've heard they can push > 300K+ IOPs.
> > So I would just ignore performance discussion because I don't think
> > folks have done even simple lame experiments in the last 1 year. Or
> > may be I'm completely wrong and so please enlighten me so that I can
> > re-run the tests.
> >
> >
> >> Bart.
> >>
> > Chetan Loke
> >
> 
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