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

[Andrea Vai]

Il giorno lun, 23/12/2019 alle 11.26 -0500, Theodore Y. Ts'o ha
scritto:
> On Mon, Dec 23, 2019 at 09:08:28PM +0800, Ming Lei wrote:
> > 
> > From the above trace:
> > 
> >   b'blk_mq_sched_request_inserted'
> >   b'blk_mq_sched_request_inserted'
> >   b'dd_insert_requests'
> >   b'blk_mq_sched_insert_requests'
> >   b'blk_mq_flush_plug_list'
> >   b'blk_flush_plug_list'
> >   b'io_schedule_prepare'
> >   b'io_schedule'
> >   b'rq_qos_wait'
> >   b'wbt_wait'
> >   b'__rq_qos_throttle'
> >   b'blk_mq_make_request'
> >   b'generic_make_request'
> >   b'submit_bio'
> >   b'ext4_io_submit'
> >   b'ext4_writepages'
> >   b'do_writepages'
> >   b'__filemap_fdatawrite_range'
> >   b'ext4_release_file'
> >   b'__fput'
> >   b'task_work_run'
> >   b'exit_to_usermode_loop'
> >   b'do_syscall_64'
> >   b'entry_SYSCALL_64_after_hwframe'
> >     b'cp' [19863]
> >     4400
> > 
> > So this write is clearly from 'cp' process, and it should be one
> > ext4 fs issue.
> 
> We need a system call trace of the cp process, to understand what
> system call is resulting in fput, (eg., I assume it's close(2) but
> let's be sure), and often it's calling that system call.
> 
> What cp process is it?  Is it from shellutils?  Is it from busybox?
> 
>      		   	      	   		- Ted

I run the cp command from a bash script, or from a bash shell. I don't
know if this answer your question, otherwise feel free to tell me a
way to find the answer to give you.

Thanks,
Andrea