Re: [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0% regression

Damien Le Moal
2022-08-12T18:27:29Z

On 2022/08/12 10:17, John Garry wrote:
> On 12/08/2022 16:41, Damien Le Moal wrote:
>>>> we noticed the commit is already in mainline now, and in our tests, there is
>>>> still similar regression and also on other platforms.
>>>> could you guide us how to check "which host driver is being used for this
>>>> test"? hope to supply some useful information.
>>>>
>>> For me, a complete kernel log may help.
>> I had a look yesterday with my test rig. I did not see any difference in the
>> default max_sectors_kb values for various drives between 5.18 and 5.19 (current
>> linus tree). The test machine has 2 AHCI adapters: Intel and Marvell. Both use
>> the regular AHCI driver. I have another rig with different ATA adapters but it
>> is powered down and I am traveling... So cannot test that right now.
>>
>
> FWIW, on QEMU I get a difference for IDE disk for ata_piix host.
>
> Interestingly ata dev max_sectors kb also gets capped from 32MB (LBA48)
> -> 256KB due to swiotlb max mapping size. (It would be capped by shost
> default max sectors 512KB without that swiotlb limit). I assume capping
> due to swiotlb limit is not occuring on Oliver's machine.

Yes, I was suspecting that we may be seeing a difference for anything that is
not AHCI, e.g. with other drivers.

But that seems to be the correct thing to do, no ? How was this working before
without applying the swiotlb limit ?

>
> thanks,
> John
>
> [ 1.497233] ata7: found unknown device (class 0)
> [ 1.498341] ata7.00: ATA-7: QEMU HARDDISK, 2.5+, max UDMA/100
> [ 1.499030] ata7.00: 209716 sectors, multi 16: LBA48
> [ 1.623795] ata2: SATA link down (SStatus 0 SControl 300)
> [ 1.624633] ata1: SATA link down (SStatus 0 SControl 300)
> [ 1.633395] ata6: SATA link down (SStatus 0 SControl 300)
> [ 1.634200] ata5: SATA link down (SStatus 0 SControl 300)
> [ 1.635094] ata4: SATA link down (SStatus 0 SControl 300)
> [ 1.635887] ata3: SATA link down (SStatus 0 SControl 300)
> [ 1.636748] scsi 6:0:0:0: Direct-Access ATA QEMU HARDDISK
> 2.5+ PQ: 0 ANSI: 5
> [ 1.641298] sd 6:0:0:0: [sda] 209716 512-byte logical blocks: (107
> MB/102 MiB)
> [ 1.642188] sd 6:0:0:0: [sda] Write Protect is off
> [ 1.642770] sd 6:0:0:0: [sda] Mode Sense: 00 3a 00 00
> [ 1.642783] sd 6:0:0:0: [sda] Write cache: enabled, read cache:
> enabled, doesn't support DPO or FUA
> [ 1.644149] sd 6:0:0:0: [sda] Preferred minimum I/O size 512 bytes
> [ 1.645142] sd 6:0:0:0: Attached scsi generic sg0 type 0
> [ 1.655145] sd 6:0:0:0: [sda] Attached SCSI disk

--
Damien Le Moal
Western Digital Research