> Il giorno 14 feb 2018, alle ore 08:15, Mike Galbraith <efault@xxxxxx> ha scritto: > > On Wed, 2018-02-14 at 08:04 +0100, Mike Galbraith wrote: >> >> And _of course_, roughly two minutes later, IO stalled. > > P.S. > > crash> bt 19117 > PID: 19117 TASK: ffff8803d2dcd280 CPU: 7 COMMAND: "kworker/7:2" > #0 [ffff8803f7207bb8] __schedule at ffffffff81595e18 > #1 [ffff8803f7207c40] schedule at ffffffff81596422 > #2 [ffff8803f7207c50] io_schedule at ffffffff8108a832 > #3 [ffff8803f7207c60] blk_mq_get_tag at ffffffff8129cd1e > #4 [ffff8803f7207cc0] blk_mq_get_request at ffffffff812987cc > #5 [ffff8803f7207d00] blk_mq_alloc_request at ffffffff81298a9a > #6 [ffff8803f7207d38] blk_get_request_flags at ffffffff8128e674 > #7 [ffff8803f7207d60] scsi_execute at ffffffffa0025b58 [scsi_mod] > #8 [ffff8803f7207d98] scsi_test_unit_ready at ffffffffa002611c [scsi_mod] > #9 [ffff8803f7207df8] sd_check_events at ffffffffa0212747 [sd_mod] > #10 [ffff8803f7207e20] disk_check_events at ffffffff812a0f85 > #11 [ffff8803f7207e78] process_one_work at ffffffff81079867 > #12 [ffff8803f7207eb8] worker_thread at ffffffff8107a127 > #13 [ffff8803f7207f10] kthread at ffffffff8107ef48 > #14 [ffff8803f7207f50] ret_from_fork at ffffffff816001a5 > crash> This has evidently to do with tag pressure. I've looked for a way to easily reduce the number of tags online, so as to put your system in the bad spot deterministically. But at no avail. Does anyone know a way to do it? Thanks, Paolo