Re: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest]

Nick Piggin
2003-02-10T12:07:51Z

Andrea Arcangeli wrote:

>On Mon, Feb 10, 2003 at 03:48:08AM -0800, Andrew Morton wrote:
>
>>Andrea Arcangeli <andrea@suse.de> wrote:
>>
>>>It's the readahead in my tree that allows the reads to use the max scsi
>>>command size. It has nothing to do with the max scsi command size
>>>itself.
>>>
>>Oh bah.
>>
>>- *max_ra++ = vm_max_readahead;
>>+ *max_ra = ((128*4) >> (PAGE_SHIFT - 10)) - 1;
>>
>>
>>Well of course that will get bigger bonnie numbers, for exactly the reasons
>>I've explained. It will seek between files after every 512k rather than
>>after every 128k.
>>
>
>NOTE: first there is no seek at all in the benchmark we're talking
>about, no idea why you think there are seeks. This is not tiobench, this
>is bonnie sequential read.
>
Yes, Andrew obviously missed this... Anyway, could it be due to
a big stripe size and hitting more disks in the RAID? How does
a single SCSI disk perform here, Andrea?