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

John Garry
2022-08-16T10:50:56Z

On 16/08/2022 07:57, Oliver Sang wrote:
>>> For me, a complete kernel log may help.
>> and since only 1HDD, the output of the following would be helpful:
>>
>> /sys/block/sda/queue/max_sectors_kb
>> /sys/block/sda/queue/max_hw_sectors_kb
>>
>> And for 5.19, if possible.
> for commit
> 0568e61225 ("ata: libata-scsi: cap ata_device->max_sectors according to shost->max_sectors")
>
> root@lkp-icl-2sp1 ~# cat /sys/block/sda/queue/max_sectors_kb
> 512
> root@lkp-icl-2sp1 ~# cat /sys/block/sda/queue/max_hw_sectors_kb
> 512
>
> for both commit
> 4cbfca5f77 ("scsi: scsi_transport_sas: cap shost opt_sectors according to DMA optimal limit")
> and v5.19
>
> root@lkp-icl-2sp1 ~# cat /sys/block/sda/queue/max_sectors_kb
> 1280
> root@lkp-icl-2sp1 ~# cat /sys/block/sda/queue/max_hw_sectors_kb
> 32767
>

thanks, I appreciate this.

From the dmesg, I see 2x SATA disks - I was under the impression that
the system only has 1x.

Anyway, both drives show LBA48, which means the large max hw sectors at
32767KB:
[ 31.129629][ T1146] ata6.00: 1562824368 sectors, multi 1: LBA48 NCQ
(depth 32)

So this is what I suspected: we are capped from the default shost max
sectors (1024 sectors).

This seems like the simplest fix for you:

--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -1382,7 +1382,8 @@ extern const struct attribute_group
*ata_common_sdev_groups[];
.proc_name = drv_name, \
.slave_destroy = ata_scsi_slave_destroy, \
.bios_param = ata_std_bios_param, \
- .unlock_native_capacity = ata_scsi_unlock_native_capacity
+ .unlock_native_capacity = ata_scsi_unlock_native_capacity,\
+ .max_sectors = ATA_MAX_SECTORS_LBA48

A concern is that other drivers which use libata may have similar
issues, as they use default in SCSI_DEFAULT_MAX_SECTORS for max_sectors:
hisi_sas
pm8001
aic9xxx
mvsas
isci

So they may be needlessly hobbled for some SATA disks. However I have a
system with hisi_sas controller and attached LBA48 disk. I tested
performance for v5.19 vs 6.0 and it was about the same for fio rw=read @
~120K IOPS. I can test this further.

Thanks,
John