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

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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



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