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Diffstat (limited to 'results/classifier/gemma3:12b/device/1926231')
| -rw-r--r-- | results/classifier/gemma3:12b/device/1926231 | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/results/classifier/gemma3:12b/device/1926231 b/results/classifier/gemma3:12b/device/1926231 new file mode 100644 index 00000000..e05b65fe --- /dev/null +++ b/results/classifier/gemma3:12b/device/1926231 @@ -0,0 +1,38 @@ + +SCSI passthrough of SATA cdrom -> errors & performance issues + +qemu 5.0, compiled from git + +I am passing through a SATA cdrom via SCSI passthrough, with this libvirt XML: + + <hostdev mode='subsystem' type='scsi' managed='no' sgio='unfiltered' rawio='yes'> + <source> + <adapter name='scsi_host3'/> + <address bus='0' target='0' unit='0'/> + </source> + <alias name='hostdev0'/> + <address type='drive' controller='0' bus='0' target='0' unit='0'/> + </hostdev> + +It seems to mostly work, I have written discs with it, except I am getting errors that cause reads to take about 5x as long as they should, under certain circumstances. It appears to be based on the guest's read block size. + +I found that if on the guest I run, say `dd if=$some_large_file bs=262144|pv > /dev/null`, `iostat` and `pv` disagree about how much is being read by a factor of about 2. Also many kernel messages like this happen on the guest: + +[ 190.919684] sr 0:0:0:0: [sr0] tag#160 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE cmd_age=0s +[ 190.919687] sr 0:0:0:0: [sr0] tag#160 Sense Key : Aborted Command [current] +[ 190.919689] sr 0:0:0:0: [sr0] tag#160 Add. Sense: I/O process terminated +[ 190.919691] sr 0:0:0:0: [sr0] tag#160 CDB: Read(10) 28 00 00 18 a5 5a 00 00 80 00 +[ 190.919694] blk_update_request: I/O error, dev sr0, sector 6460776 op 0x0:(READ) flags 0x80700 phys_seg 5 prio class 0 + +If I change to bs=131072 the errors stop and performance is normal. + +(262144 happens to be the block size ultimately used by md5sum, which is how I got here) + +I also ran strace on the qemu process while it was happening, and noticed SG_IO calls like this: + +21748 10:06:29.330910 ioctl(22, SG_IO, {interface_id='S', dxfer_direction=SG_DXFER_FROM_DEV, cmd_len=10, cmdp="\x28\x00\x00\x12\x95\x5a\x00\x00\x80\x00", mx_sb_len=252, iovec_count=0, dxfer_len=262144, timeout=4294967295, flags=SG_FLAG_DIRECT_IO <unfinished ...> +21751 10:06:29.330976 ioctl(22, SG_IO, {interface_id='S', dxfer_direction=SG_DXFER_FROM_DEV, cmd_len=10, cmdp="\x28\x00\x00\x12\x94\xda\x00\x00\x02\x00", mx_sb_len=252, iovec_count=0, dxfer_len=4096, timeout=4294967295, flags=SG_FLAG_DIRECT_IO <unfinished ...> +21749 10:06:29.331586 ioctl(22, SG_IO, {interface_id='S', dxfer_direction=SG_DXFER_FROM_DEV, cmd_len=10, cmdp="\x28\x00\x00\x12\x94\xdc\x00\x00\x02\x00", mx_sb_len=252, iovec_count=0, dxfer_len=4096, timeout=4294967295, flags=SG_FLAG_DIRECT_IO <unfinished ...> +[etc] + +I suspect qemu is the culprit because I have tried a 4.19 guest kernel as well as a 5.9 one, with the same result. \ No newline at end of file |