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 Thanks, and bye, Andrea