[lvm-devel] [PATCH 1/6] Pool locking code
Zdenek Kabelac
zkabelac at redhat.com
Wed Mar 23 17:29:38 UTC 2011
Dne 23.3.2011 17:33, Zdenek Kabelac napsal(a):
> Dne 23.3.2011 16:57, Zdenek Kabelac napsal(a):
>> Dne 23.3.2011 16:13, Joe Thornber napsal(a):
>>> On Wed, 2011-03-23 at 15:54 +0100, Zdenek Kabelac wrote:
>>>> Forget to answer the size question - >8MB is allocated by the VG
>>>> mempool when
>>>> set of simple linear 7200LVs on 1 PV are in use.
>>>
>>> So I think each snapshot/restore of a VG pool of that size is going to
>>> take ~0.1 seconds. So now my question is how many times are we
>>> expecting to happen during a typical tool invocation? Your previous
>>> reply suggested it happens just once?
>>
>>
>> If there would be just 1 vg read for 7200 activate call - obviously I'd not
>> need to play with this dm_pool locking :)
>>
>> So there is 7200 vg reads - which will use this one locked pool with my patch set:
>>
>> To give some time info here
>> (using my unoptimized gcc debug build on C2D 2.2GHz - but with few more
>> patches applied than current upstream)
>>
>> Deactivate 7200LV (7200 already active)
>> real 1m16.140s
>> user 0m5.686s
>> sys 0m31.410s
>>
>>
>> Deactivate 7200LV (non active)
>> real 0m2.121s
>> user 0m1.083s
>> sys 0m1.032s
>>
>>
>> Activate 7200 (non active)
>> real 2m19.324s
>> user 0m6.503s
>> sys 1m30.785s
>>
>> Activate 7200 (7200 already active)
>> real 0m10.945s
>> user 0m1.422s
>> sys 0m9.502s
>>
>
> I think good example could be this - when I disable mprotect-ing in my
> patchset - and enable crc checking with each dm_pool_restore (which should be
> similar to memcpy) (otherwise crc is checked only with final pool unlock)
>
> Deactivate 7200LV
> real 1m45.353s
> user 0m38.128s
> sys 0m27.395s
>
> Deactivate 7200LV
> real 0m36.948s
> user 0m35.284s
> sys 0m1.642s
>
> Activate 7200 (non active)
> real 2m31.065s
> user 0m37.740s
> sys 1m18.481s
>
> (here could be observed - thet mprotecting takes 12s)
>
> Activate 7200 (7200 already active)
> real 0m52.188s
> user 0m35.570s
> sys 0m16.563s
>
>
>
> So I'd estimate like 33seconds would be wasted.
>
> --
>
> And to complete the picture - crc only with unlock - and without pool
> mprotect-ing - assuming this would be normal work.
>
> Deactivate 7200LV
> real 1m9.989s
> user 0m4.584s
> sys 0m26.882s
>
> Deactivate 7200LV
> real 0m2.119s
> user 0m1.087s
> sys 0m1.025s
>
> Activate 7200 (non active)
> real 2m11.363s
> user 0m4.696s
> sys 1m15.393s
>
> Activate 7200 (7200 already active)
> real 0m11.127s
> user 0m1.392s
> sys 0m9.669s
>
And as the implementation of memcpy instead of crc was rather very simple -
here are exact numbers with memcpy (memcpy being somewhat faster then crc):
Deactivate 7200LV (7200 already active)
real 1m32.725s
user 0m24.828s
sys 0m27.213s
Deactivate 7200LV (non active)
real 0m20.486s
user 0m18.239s
sys 0m2.236s
Activate 7200 (non active)
real 2m33.219s
user 0m24.777s
sys 1m19.996s
Activate 7200 (7200 already active)
real 0m36.627s
user 0m18.474s
sys 0m18.065s
Zdenek
More information about the lvm-devel
mailing list