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

Andrea Vai
2019-12-23T16:29:32Z

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