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SubjectRe: Some NCQ numbers...
Tejun Heo wrote:
> Hello,
>
> Michael Tokarev wrote:
>> Well. It looks like the results does not depend on the
>> elevator. Originally I tried with deadline, and just
>> re-ran the test with noop (hence the long delay with
>> the answer) - changing linux elevator changes almost
>> nothing in the results - modulo some random "fluctuations".
>
> I see. Thanks for testing.

Here are actual results - the tests were still running when
I replied yesterday.

Again, this is Seagate ST3250620AS "desktop" drive, 7200RPM,
16Mb cache, 250Gb capacity. The tests were performed with
queue depth = 64 (on mptsas), drive write cache is turned
off.

noop scheduler:

BlkSz Trd linRd rndRd linWr rndWr rndR/W
4k 1 12.8 0.3 0.4 0.3 0.1/ 0.1
4 0.3 0.3 0.1/ 0.1
32 0.3 0.3 0.1/ 0.1
8k 1 24.6 0.6 0.9 0.6 0.3/ 0.3
4 0.6 0.6 0.3/ 0.3
32 0.6 0.6 0.3/ 0.3
16k 1 41.3 1.2 1.8 1.1 0.6/ 0.6
4 1.2 1.1 0.6/ 0.6
32 1.2 1.1 0.6/ 0.6
32k 1 58.4 2.2 3.5 2.1 1.1/ 1.1
4 2.3 2.1 1.1/ 1.1
32 2.3 2.1 1.1/ 1.1
128k 1 80.4 8.1 12.5 7.2 3.8/ 3.8
4 8.1 7.2 3.8/ 3.8
32 8.1 7.2 3.8/ 3.8
1024k 1 80.5 33.9 33.8 24.5 14.3/14.3
4 34.1 24.6 14.3/14.2
32 34.2 24.6 14.4/14.2

deadline scheduler:

BlkSz Trd linRd rndRd linWr rndWr rndR/W
4k 1 12.8 0.3 0.4 0.3 0.1/ 0.1
4 0.3 0.3 0.1/ 0.1
32 0.3 0.3 0.1/ 0.1
8k 1 24.5 0.6 0.9 0.6 0.3/ 0.3
4 0.6 0.6 0.3/ 0.3
32 0.6 0.6 0.3/ 0.3
16k 1 41.3 1.2 1.8 1.1 0.6/ 0.6
4 1.2 1.1 0.6/ 0.6
32 1.2 1.1 0.6/ 0.6
32k 1 57.7 2.3 3.4 2.1 1.1/ 1.1
4 2.3 2.1 1.1/ 1.1
32 2.3 2.1 1.1/ 1.1
128k 1 79.4 8.1 12.5 7.2 3.8/ 3.8
4 8.1 7.3 3.8/ 3.8
32 8.2 7.3 3.9/ 3.8
1024k 1 79.4 33.7 33.8 24.5 14.2/14.2
4 33.9 24.6 14.3/14.2
32 33.4 24.4 17.0/10.5

[]
>> By the way, Seagate announced Barracuda ES 2 series
>> (in range 500..1200Gb if memory serves) - maybe with
>> those, NCQ will work better?
>
> No one would know without testing.

Sure thing. I guess I'll set up a web page with all
the results so far, in a hope someday it will be more
complete (we don't have many different drives to test,
but others do).

By the way. Both SATA drives we have are single-platter
ones (with 500Gb models they've 2 platters, and 750Gb
ones are with 3 platters), while all SCSI drives I
tested have more than one platters. Maybe this is
yet another reason for NCQ failing.

And another note. I heard somewhere that Seagate for
one prohibits publishing of tests like this, however
I haven't signed any NDAs and somesuch when purchased
their drives in a nearest computer store... ;)

>> Or maybe it's libata which does not implement NCQ
>> "properly"? (As I shown before, with almost all
>> ol'good SCSI drives TCQ helps alot - up to 2x the
>> difference and more - with multiple I/O threads)
>
> Well, what the driver does is minimal. It just passes through all the
> commands to the harddrive. After all, NCQ/TCQ gives the harddrive more
> responsibility regarding request scheduling.

Oh well, I see.... :(

/mjt
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