On Wed, Jul 03, 2019 at 07:11:17AM +0200, Andrea Vai wrote:
> On 03/07/19 10:01:23, Ming Lei wrote:
> > On Wed, Jul 03, 2019 at 12:39:31AM +0200, Andrea Vai wrote:
> > > On 02/07/19 20:01:13, Ming Lei wrote:
> > > > On Tue, Jul 02, 2019 at 12:46:45PM +0200, Andrea Vai wrote:
> > > > > Hi,
> > > > > I have a problem writing data to a USB pendrive, and it seems
> > > > > kernel-related. With the help of Greg an Alan (thanks) and some
> > > > > bisect, I found out the offending commit being
> > > > >
> > > > > commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6
> > > > >
> > > > > [...]
> > > > >
> > > >
> > > > One possible reason may be related with too small 'nr_requests', could
> > > > you apply the following command and see if any difference can be made?
> > > >
> > > > echo 32 > /sys/block/sdN/queue/nr_requests
> > >
> > > I applied it (echo 32 > /sys/block/sdf/queue/nr_requests), ran the test again, and still failed. I assumed I didn't have to build the kernel again, did I? (sorry but I am not skilled)
> > >
> >
> > You don't need to build kernel.
> >
> > I just run same write test on one slow usb drive in my laptop, which
> > runs '5.1.11-200.fc29.x86_64', and can't reproduce your issue, maybe it
> > depends on your drive.
> >
> > Could you collect the queue limits sysfs log via the following command?
> >
> > find /sys/block/sdN/queue -type f -exec grep -aH . {} \;
> >
>
> # find /sys/block/sdf/queue -type f -exec grep -aH . {} ;
> /sys/block/sdf/queue/io_poll_delay:-1
> /sys/block/sdf/queue/max_integrity_segments:0
> /sys/block/sdf/queue/zoned:none
> /sys/block/sdf/queue/scheduler:[mq-deadline] none
> /sys/block/sdf/queue/io_poll:0
> /sys/block/sdf/queue/discard_zeroes_data:0
> /sys/block/sdf/queue/minimum_io_size:512
> /sys/block/sdf/queue/nr_zones:0
> /sys/block/sdf/queue/write_same_max_bytes:0
> /sys/block/sdf/queue/max_segments:2048
> /sys/block/sdf/queue/dax:0
> /sys/block/sdf/queue/physical_block_size:512
> /sys/block/sdf/queue/logical_block_size:512
> /sys/block/sdf/queue/io_timeout:30000
> /sys/block/sdf/queue/nr_requests:2
> /sys/block/sdf/queue/write_cache:write through/sys/block/sdf/queue/max_segment_size:4294967295
> /sys/block/sdf/queue/rotational:1
> /sys/block/sdf/queue/discard_max_bytes:0
> /sys/block/sdf/queue/add_random:1
> /sys/block/sdf/queue/discard_max_hw_bytes:0
> /sys/block/sdf/queue/optimal_io_size:0
> /sys/block/sdf/queue/chunk_sectors:0
> /sys/block/sdf/queue/iosched/front_merges:1
> /sys/block/sdf/queue/iosched/read_expire:500
> /sys/block/sdf/queue/iosched/fifo_batch:16
> /sys/block/sdf/queue/iosched/write_expire:5000/sys/block/sdf/queue/iosched/writes_starved:2
> /sys/block/sdf/queue/read_ahead_kb:128
> /sys/block/sdf/queue/max_discard_segments:1
> /sys/block/sdf/queue/write_zeroes_max_bytes:0
> /sys/block/sdf/queue/nomerges:0
> /sys/block/sdf/queue/wbt_lat_usec:75000
> /sys/block/sdf/queue/fua:0
> /sys/block/sdf/queue/discard_granularity:0
> /sys/block/sdf/queue/rq_affinity:1
> /sys/block/sdf/queue/max_sectors_kb:120
> /sys/block/sdf/queue/hw_sector_size:512
> /sys/block/sdf/queue/max_hw_sectors_kb:120
> /sys/block/sdf/queue/iostats:1
The above is basically same with my USB drive's queue setting, and looks
all are fine.
BTW, 'rotational' shouldn't be set for USB drive, except for USB HDD,
but that shouldn't be related with your issue.
Then could you install bcc package and collect the IO trace?
sudo /usr/share/bcc/tools/biosnoop | grep sdN
sdN is your USB disk device name.
Thanks,
Ming
