rawhide ext4/virtio FS performance hit (10x slower) ?

Jim Meyering jim at meyering.net
Mon May 7 14:41:13 UTC 2012


Josh Boyer wrote:
> On Mon, May 7, 2012 at 8:43 AM, Jim Meyering <jim at meyering.net> wrote:
>> Today I noticed that some tests from coreutils' test suite
>> were taking far longer than they used to on rawhide.
>> For example, run this command in an empty directory:
>>
>>  seq 200000|env time xargs touch
>>
>> it takes < 5s on F17 3.3.4-1.fc17.x86_64 ext4/sdb8/SSD, yet
>> it takes 47s on rawhide 3.4.0-0.rc5.git5.1.fc18.x86_64 ext4/vda1/SSD
>>
>> 10x performance hit... ouch.
>>
>> Does anyone know why?
>
> Rawhide has all the kernel debug options turned on.  It isn't
> worthwhile doing a comparison when those are enabled.  You could try
> again with the first -rc6 build that shows up, as that will have the
> options disabled.

Thanks.  Will do.

I knew about the kernel debug options, but didn't realize they
could make such a large difference.


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