Re: submit_bh leaves interrupts on upon return

["Jeff V. Merkey" <jmerkey@drdos.com>]

Linus Torvalds wrote:

>On Thu, 3 Jun 2004, Jens Axboe wrote:
>
>  
>
>>On Thu, Jun 03 2004, Jeff V. Merkey wrote:
>>    
>>
>>>Sounds like I need to move to 2.6. I noticed the elevator is coalescing 
>>>quite well, and since I am posting mostly continguous runs of sectors, 
>>>what ends up at the adapter level would probably not change much much 
>>>between 2.4 and 2.6 since I am maxing out the driver request queues as 
>>>it is (255 pending requests of 32 scatter/gather elements of 256 sector 
>>>runs). 2.6 might help but I suspect it will only help alleviate the 
>>>submission overhead, and not make much difference on performance since 
>>>the 3Ware card does have an upward limit on outstanding I/O requests.
>>>      
>>>
>>That's correct, it just helps you diminish the submission overhead by
>>pushing down 256 sector entities in one go. So as long as you're io
>>bound it won't give you better io performance, of course. If you are
>>doing 400MiB/sec it should help you out, though.
>>    
>>
>
>Well, if Jeff does almost exclusively contiguous stuff and submits them in
>order, then the coalescing will make sure that even on 2.4.x the queues
>don't get too long, and he probably won't see the pathological cases.
>
>		Linus
>-
>
Linus,

This seems to be the case.

Jeff




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