Re: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6

From: Andrea Vai <andrea.vai@unipv.it>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-usb@vger.kernel.org, linux-scsi@vger.kernel.org,
	Himanshu Madhani <himanshu.madhani@cavium.com>,
	Hannes Reinecke <hare@suse.com>, Omar Sandoval <osandov@fb.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Alan Stern <stern@rowland.harvard.edu>
Subject: Re: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6
Date: Wed, 3 Jul 2019 07:11:17 +0200	[thread overview]
Message-ID: <20190703051117.GA6458@brian.unipv.it> (raw)
In-Reply-To: <20190703020119.GA23872@ming.t460p>

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