Il giorno mar, 24/12/2019 alle 09.32 +0800, Ming Lei ha scritto: > On Mon, Dec 23, 2019 at 03:02:35PM +0100, Andrea Vai wrote: > > Il giorno lun, 23/12/2019 alle 21.08 +0800, Ming Lei ha scritto: > > > On Mon, Dec 23, 2019 at 12:22:45PM +0100, Andrea Vai wrote: > > > > Il giorno mer, 18/12/2019 alle 17.48 +0800, Ming Lei ha > scritto: > > > > > On Wed, Dec 18, 2019 at 09:25:02AM +0100, Andrea Vai wrote: > > > > > > Il giorno gio, 12/12/2019 alle 05.33 +0800, Ming Lei ha > > > scritto: > > > > > > > On Wed, Dec 11, 2019 at 11:07:45AM -0500, Theodore Y. > Ts'o > > > > > wrote: > > > > > > > > On Wed, Dec 11, 2019 at 12:00:58PM +0800, Ming Lei > wrote: > > > > > > > > > I didn't reproduce the issue in my test environment, > and > > > > > follows > > > > > > > > > Andrea's test commands[1]: > > > > > > > > > > > > > > > > > > mount UUID=$uuid /mnt/pendrive 2>&1 |tee -a > $logfile > > > > > > > > > SECONDS=0 > > > > > > > > > cp $testfile /mnt/pendrive 2>&1 |tee -a $logfile > > > > > > > > > umount /mnt/pendrive 2>&1 |tee -a $logfile > > > > > > > > > > > > > > > > > > The 'cp' command supposes to open/close the file > just > > > once, > > > > > > > however > > > > > > > > > ext4_release_file() & write pages is observed to run > for > > > > > 4358 > > > > > > > times > > > > > > > > > when executing the above 'cp' test. > > > > > > > > > > > > > > > > Why are we sure the ext4_release_file() / _fput() is > > > coming > > > > > from > > > > > > > the > > > > > > > > cp command, as opposed to something else that might be > > > running > > > > > on > > > > > > > the > > > > > > > > system under test? _fput() is called by the kernel > when > > > the > > > > > last > > > > > > > > > > > > > > Please see the log: > > > > > > > > > > > > > > > > > > > > > > > https://lore.kernel.org/linux-scsi/3af3666920e7d46f8f0c6d88612f143ffabc743c.camel@xxxxxxxx/2-log_ming.zip > > > > > > > > > > > > > > Which is collected by: > > > > > > > > > > > > > > #!/bin/sh > > > > > > > MAJ=$1 > > > > > > > MIN=$2 > > > > > > > MAJ=$(( $MAJ << 20 )) > > > > > > > DEV=$(( $MAJ | $MIN )) > > > > > > > > > > > > > > /usr/share/bcc/tools/trace -t -C \ > > > > > > > 't:block:block_rq_issue (args->dev == '$DEV') "%s %d > > > %d", > > > > > args- > > > > > > > >rwbs, args->sector, args->nr_sector' \ > > > > > > > 't:block:block_rq_insert (args->dev == '$DEV') "%s > %d > > > %d", > > > > > args- > > > > > > > >rwbs, args->sector, args->nr_sector' > > > > > > > > > > > > > > $MAJ:$MIN points to the USB storage disk. > > > > > > > > > > > > > > From the above IO trace, there are two write paths, one > is > > > from > > > > > cp, > > > > > > > another is from writeback wq. > > > > > > > > > > > > > > The stackcount trace[1] is consistent with the IO trace > log > > > > > since it > > > > > > > only shows two IO paths, that is why I concluded that > the > > > write > > > > > done > > > > > > > via > > > > > > > ext4_release_file() is from 'cp'. > > > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > https://lore.kernel.org/linux-scsi/320b315b9c87543d4fb919ecbdf841596c8fbcea.camel@xxxxxxxx/2-log_ming_20191129_150609.zip > > > > > > > > > > > > > > > reference to a struct file is > released. (Specifically, if > > > you > > > > > > > have a > > > > > > > > fd which is dup'ed, it's only when the last fd > > > corresponding > > > > > to > > > > > > > the > > > > > > > > struct file is closed, and the struct file is about to > be > > > > > > > released, > > > > > > > > does the file system's f_ops->release function get > > > called.) > > > > > > > > > > > > > > > > So the first question I'd ask is whether there is > anything > > > > > else > > > > > > > going > > > > > > > > on the system, and whether the writes are happening to > the > > > USB > > > > > > > thumb > > > > > > > > drive, or to some other storage device. And if there > is > > > > > something > > > > > > > > else which is writing to the pendrive, maybe that's > why no > > > one > > > > > > > else > > > > > > > > has been able to reproduce the OP's complaint.... > > > > > > > > > > > > > > OK, we can ask Andrea to confirm that via the following > > > trace, > > > > > which > > > > > > > will add pid/comm info in the stack trace: > > > > > > > > > > > > > > /usr/share/bcc/tools/stackcount > > > blk_mq_sched_request_inserted > > > > > > > > > > > > > > Andrew, could you collect the above log again when > running > > > > > new/bad > > > > > > > kernel for confirming if the write done by > > > ext4_release_file() > > > > > is > > > > > > > from > > > > > > > the 'cp' process? > > > > > > > > > > > > You can find the stackcount log attached. It has been > produced > > > by: > > > > > > > > > > > > - /usr/share/bcc/tools/stackcount > > > blk_mq_sched_request_inserted > > > > > > trace.log > > > > > > - wait some seconds > > > > > > - run the test (1 copy trial), wait for the test to > finish, > > > wait > > > > > some seconds > > > > > > - stop the trace (ctrl+C) > > > > > > > > > > Thanks for collecting the log, looks your 'stackcount' > doesn't > > > > > include > > > > > comm/pid info, seems there is difference between your bcc > and > > > > > my bcc in fedora 30. > > > > > > > > > > Could you collect above log again via the following command? > > > > > > > > > > /usr/share/bcc/tools/stackcount -P -K > t:block:block_rq_insert > > > > > > > > > > which will show the comm/pid info. > > > > > > > > ok, attached (trace_20191219.txt), the test (1 trial) took > 3684 > > > > seconds. > > > > > > 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. > > > > > > Ted, can you take a look at this issue? > > > > > > > > > > > > > I also tried the usual test with btrfs and xfs. Btrfs > behavior > > > > > looks > > > > > > "good". xfs seems sometimes better, sometimes worse, I > would > > > say. > > > > > I > > > > > > don't know if it matters, anyway you can also find the > results > > > of > > > > > the > > > > > > two tests (100 trials each). Basically, btrfs is always > > > between 68 > > > > > and > > > > > > 89 seconds, with a cyclicity (?) with "period=2 trials". > xfs > > > looks > > > > > > almost always very good (63-65s), but sometimes "bad" > (>300s). > > > > > > > > > > If you are interested in digging into this one, the > following > > > trace > > > > > should be helpful: > > > > > > > > > > > > > > https://lore.kernel.org/linux-scsi/f38db337cf26390f7c7488a0bc2076633737775b.camel@xxxxxxxx/T/#m5aa008626e07913172ad40e1eb8e5f2ffd560fc6 > > > > > > > > > > > > > Attached: > > > > - trace_xfs_20191223.txt (7 trials, then aborted while doing > the > > > 8th), > > > > times to complete: > > > > 64s > > > > 63s > > > > 64s > > > > 833s > > > > 1105s > > > > 63s > > > > 64s > > > > > > oops, looks we have to collect io insert trace with the > following > > > bcc script > > > on xfs for confirming if there is similar issue with ext4, could > you > > > run > > > it again on xfs? And only post the trace done in case of slow > 'cp'. > > > > > > > > > #!/bin/sh > > > > > > MAJ=$1 > > > MIN=$2 > > > MAJ=$(( $MAJ << 20 )) > > > DEV=$(( $MAJ | $MIN )) > > > > > > /usr/share/bcc/tools/trace -t -C \ > > > 't:block:block_rq_issue (args->dev == '$DEV') "%s %d %d", > args- > > > >rwbs, args->sector, args->nr_sector' \ > > > 't:block:block_rq_insert (args->dev == '$DEV') "%s %d %d", > args- > > > >rwbs, args->sector, args->nr_sector' > > > > > > > > here it is (1 trial, 313 seconds to finish) > > The above log shows similar issue with ext4 since there is another > writeback IO path from 'cp' process. And the following trace can > show if > it is same with ext4's issue: > > /usr/share/bcc/tools/stackcount -P -K t:block:block_rq_insert sorry, also here please tell me which conditions should I use to run the test (ext4 or xfs? slow run or not important?) Thanks, Andrea
