On 16/08/2022 16:42, Damien Le Moal wrote:
On 2022/08/16 3:35, John Garry wrote:
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
This is crazy large (65535 x 512 B sectors) and never result in that being
exposed as the actual max_sectors_kb since other limits will apply first
(mapping size).
Here is how I read values from above for max_sectors_kb and
max_hw_sectors_kb:
v5.19 + 0568e61225 : 512/512
v5.19 + 0568e61225 + 4cbfca5f77 : 512/512
v5.19: 1280/32767
They are want makes sense to me, at least.
Oliver, can you confirm this? Thanks!
On this basis, it appears that max_hw_sectors_kb is getting capped from
scsi default @ 1024 sectors by commit 0568e61225. If it were getting
capped by swiotlb mapping limit then that would give us 512 sectors -
this value is fixed.
So for my SHT change proposal I am just trying to revert to previous
behaviour in 5.19 - make max_hw_sectors_kb crazy big again.
The regression may come not from commands becoming tiny, but from the fact that
after the patch, max_sectors_kb is too large,
I don't think it is, but need confirmation.
causing a lot of overhead with
qemu swiotlb mapping and slowing down IO processing.
Above, it can be seen that we ed up with max_sectors_kb being 1280, which is the
default for most scsi disks (including ATA drives). That is normal. But before
that, it was 512, which likely better fits qemu swiotlb and does not generate
Again, I don't think this this is the case. Need confirmation.
overhead. So the above fix will not change anything I think...
Thanks,
John
