linux-kernel - Re: [PATCH 0/3] Enable multiple MSI feature in pSeries

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Date:	Mon, 04 Feb 2013 14:23:00 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	Mike Qiu <qiudayu@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de
Subject: Re: [PATCH 0/3] Enable multiple MSI feature in pSeries

On Tue, 2013-01-15 at 15:38 +0800, Mike Qiu wrote:
> Currently, multiple MSI feature hasn't been enabled in pSeries,
> These patches try to enbale this feature.

Hi Mike,

> These patches have been tested by using ipr driver, and the driver patch
> has been made by Wen Xiong <wenxiong@...ux.vnet.ibm.com>:

So who wrote these patches? Normally we would expect the original author
to post the patches if at all possible.

> [PATCH 0/7] Add support for new IBM SAS controllers

I would like to see the full series, including the driver enablement.

> Test platform: One partition of pSeries with one cpu core(4 SMTs) and 
>                RAID bus controller: IBM PCI-E IPR SAS Adapter (ASIC) in POWER7
> OS version: SUSE Linux Enterprise Server 11 SP2  (ppc64) with 3.8-rc3 kernel 
> 
> IRQ 21 and 22 are assigned to the ipr device which support 2 mutiple MSI.
> 
> The test results is shown by 'cat /proc/interrups':
>           CPU0       CPU1       CPU2       CPU3       
> 21:          6          5          5          5      XICS Level     host1-0
> 22:        817        814        816        813      XICS Level     host1-1

This shows that you are correctly configuring two MSIs.

But the key advantage of using multiple interrupts is to distribute load
across CPUs and improve performance. So I would like to see some
performance numbers that show that there is a real benefit for all the
extra complexity in the code.

cheers

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