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

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Date:	Wed, 16 Mar 2016 11:31:06 -0400
From:	Christopher Covington <cov@...eaurora.org>
To:	Sinan Kaya <okaya@...eaurora.org>, Hannes Reinecke <hare@...e.de>,
	linux-scsi@...r.kernel.org, timur@...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 11/10/2015 12:59 AM, Sinan Kaya wrote:
> 
> 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.

Hannes or others, any suggestions?

Thanks,
Christopher Covington

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