Messages in this thread | | | Date | Thu, 03 Jun 2004 15:17:11 -0600 | From | "Jeff V. Merkey" <> | Subject | Re: submit_bh leaves interrupts on upon return |
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Jens Axboe wrote:
>On Thu, Jun 03 2004, Jeff V. Merkey wrote: > > >>Jens Axboe wrote: >> >> >> >>>Submitting large numbers of buffer_heads from b_end_io is _nasty_, 2.4 >>>io scheduler runtime isn't exactly world champion and you are doing this >>>at hard irq time. Not a good idea. Definitely not the true path to >>>performance, unless you don't care about anything else in the system. >>> >>>At least in 2.6 you have a much faster io scheduler and the additionally >>>large bio, so you wont spend nearly as much time there if you are >>>clever. You still need process context, though, that hasn't changed. >>> >>> >>> >>> >>> >>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. > > > I'll give it a try n 2.6.
:-)
Jeff
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