linux-kernel - Re: [PATCH V2 3/3] scsi: mptxsas: offload IRQ execution

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Date:	Tue, 10 Nov 2015 00:59:54 -0500
From:	Sinan Kaya <okaya@...eaurora.org>
To:	Hannes Reinecke <hare@...e.de>, linux-scsi@...r.kernel.org,
	timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com
Cc:	agross@...eaurora.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Nagalakshmi Nandigama <nagalakshmi.nandigama@...gotech.com>,
	Praveen Krishnamoorthy <praveen.krishnamoorthy@...gotech.com>,
	Sreekanth Reddy <sreekanth.reddy@...gotech.com>,
	Abhijit Mahajan <abhijit.mahajan@...gotech.com>,
	"James E.J. Bottomley" <JBottomley@...n.com>,
	MPT-FusionLinux.pdl@...gotech.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 3/3] scsi: mptxsas: offload IRQ execution



On 11/9/2015 2:15 AM, Hannes Reinecke wrote:
> On 11/09/2015 02:57 AM, Sinan Kaya wrote:
>> The mpt2sas and mpt3sas drivers are spinning forever in
>> their IRQ handlers if there are a lot of jobs queued up
>> by the PCIe card. This handler is causing spikes for
>> the rest of the system and sluggish behavior.
>>
>> Marking all MSI interrupts as non-shared and moving the
>> MSI interrupts to thread context. This relexes the rest
>> of the system execution.
>>
> NACK.
>
> If there is a scalability issue when handling interrupts
> it should be fixed in the driver directly.
>
> Looking at the driver is should be possible to implement
> a worker thread handling the reply descriptor, and having the
> interrupt only to fetch the reply descriptor.
>

Can you go into the detail about which part of the _base_interrupt 
function needs to be executed in ISR context and which part can be 
queued up to worker thread?

I'm not familiar with the hardware or the code. That's why, I moved the 
entire ISR into the thread context.



> Cheers,
>
> Hannes
>

-- 
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a 
Linux Foundation Collaborative Project
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