Re: Software RAID checksum performance on 24 disks not even close to kernel reported

[Dan Williams <dan.j.williams@xxxxxxxxx>]

On Wed, Jun 6, 2012 at 12:19 PM, Ole Tange <ole@xxxxxxxx> wrote:
> On Wed, Jun 6, 2012 at 6:09 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>> On Wed, Jun 6, 2012 at 7:11 AM, Ole Tange <ole@xxxxxxxx> wrote:
>>> On Tue, Jun 5, 2012 at 1:14 AM, Ole Tange <ole@xxxxxxxx> wrote:
>>>
>>>> But I cannot explain why even the best performance (4600 MB/11s = 420
>>>> MB/s) is not even close to the checksum performance reported by the
>>>> kernel at boot (6196 MB/s):
>>>
>>> From the friendly people on the mailing list the answer can be summarized as:
> :
>>> In other words: What you see is normal, and it is not out of the
>>> ordinary to see md0_raid6 use 100% CPU time on a single core when
>>> using a 24 disk RAID6. Work is underway to spread the load to multiple
>>> cores using the experimental kernel parameter
>>> CONFIG_MULTICORE_RAID456.
>>
>> Don't use CONFIG_MULTICORE_RAID456, we need a different approach.
>
> Here you disagree with Brad Campbell and Igor M Podlesny. Can you
> elaborate why you do not think I should use CONFIG_MULTICORE_RAID456
> and why you do not think that approach will work?

Because I wrote the code and it doesn't work the way I want it to,
hence the experimental tag and why I need to go review Shaohua's
recent patches.

--
Dan
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