On Thu 21-03-24 16:12:52, Kemeng Shi wrote: > on 3/21/2024 1:22 AM, Jan Kara wrote: > > On Wed 20-03-24 19:02:16, Kemeng Shi wrote: > >> This series tries to improve visilibity of writeback. Patch 1 make > >> /sys/kernel/debug/bdi/xxx/stats show writeback info of whole bdi > >> instead of only writeback info in root cgroup. Patch 2 add a new > >> debug file /sys/kernel/debug/bdi/xxx/wb_stats to show per wb writeback > >> info. Patch 4 add wb_monitor.py to monitor basic writeback info > >> of running system, more info could be added on demand. Rest patches > >> are some random cleanups. More details can be found in respective > >> patches. Thanks! > >> > >> Following domain hierarchy is tested: > >> global domain (320G) > >> / \ > >> cgroup domain1(10G) cgroup domain2(10G) > >> | | > >> bdi wb1 wb2 > >> > >> /* all writeback info of bdi is successfully collected */ > >> # cat /sys/kernel/debug/bdi/252:16/stats: > >> BdiWriteback: 448 kB > >> BdiReclaimable: 1303904 kB > >> BdiDirtyThresh: 189914124 kB > >> DirtyThresh: 195337564 kB > >> BackgroundThresh: 32516508 kB > >> BdiDirtied: 3591392 kB > >> BdiWritten: 2287488 kB > >> BdiWriteBandwidth: 322248 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 2 > >> b_dirty_time: 0 > >> bdi_list: 1 > >> state: 1 > >> > >> /* per wb writeback info is collected */ > >> # cat /sys/kernel/debug/bdi/252:16/wb_stats: > >> cat wb_stats > >> WbCgIno: 1 > >> WbWriteback: 0 kB > >> WbReclaimable: 0 kB > >> WbDirtyThresh: 0 kB > >> WbDirtied: 0 kB > >> WbWritten: 0 kB > >> WbWriteBandwidth: 102400 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 0 > >> b_dirty_time: 0 > >> state: 1 > >> WbCgIno: 4284 > >> WbWriteback: 448 kB > >> WbReclaimable: 818944 kB > >> WbDirtyThresh: 3096524 kB > >> WbDirtied: 2266880 kB > >> WbWritten: 1447936 kB > >> WbWriteBandwidth: 214036 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 1 > >> b_dirty_time: 0 > >> state: 5 > >> WbCgIno: 4325 > >> WbWriteback: 224 kB > >> WbReclaimable: 819392 kB > >> WbDirtyThresh: 2920088 kB > >> WbDirtied: 2551808 kB > >> WbWritten: 1732416 kB > >> WbWriteBandwidth: 201832 kBps > >> b_dirty: 0 > >> b_io: 0 > >> b_more_io: 1 > >> b_dirty_time: 0 > >> state: 5 > >> > >> /* monitor writeback info */ > >> # ./wb_monitor.py 252:16 -c > >> writeback reclaimable dirtied written avg_bw > >> 252:16_1 0 0 0 0 102400 > >> 252:16_4284 672 820064 9230368 8410304 685612 > >> 252:16_4325 896 819840 10491264 9671648 652348 > >> 252:16 1568 1639904 19721632 18081952 1440360 > >> > >> > >> writeback reclaimable dirtied written avg_bw > >> 252:16_1 0 0 0 0 102400 > >> 252:16_4284 672 820064 9230368 8410304 685612 > >> 252:16_4325 896 819840 10491264 9671648 652348 > >> 252:16 1568 1639904 19721632 18081952 1440360 > >> ... > > > > So I'm wondering: Are you implementing this just because this looks > > interesting or do you have a real need for the functionality? Why? > Hi Jan, I added debug files to test change in [1] which changes the way how > dirty background threshold of wb is calculated. Without debug files, we could > only monitor writeback to imply that threshold is corrected. > In current patchset, debug info has not included dirty background threshold yet, > I will add it when discution of calculation of dirty background threshold in [1] > is done. > The wb_monitor.py is suggested by Tejun in [2] to improve visibility of writeback. > The script is more convenient than trace to monitor writeback behavior of the running > system. Thanks for the pointer. OK, I agree this is useful so let's have a look into the code :) Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
