On Sun, Mar 09, 2025 at 08:41:33PM +0800, Jinliang Zheng wrote: > On Tue, 4 Mar 2025 07:45:44 +1100, Dave Chinner wrote: > > On Mon, Mar 03, 2025 at 07:23:01PM +0800, Jinliang Zheng wrote: > > > When recovering a large filesystem, avoid log recover IO being > > > throttled by rq_qos_throttle(). > > > > Why? > > > > The only writes to the journal during recovery are to clear stale > > blocks - it's only a very small part of the IO that journal recovery > > typically does. What problem happens when these writes are > > throttled? > > Sorry for the late reply, I was struggling with my work. :-( > > Recently, we encountered the problem of xfs log IO being throttled in > the Linux distribution version maintained by ourselves. To be more > precise, it was indirectly throttled by the IO issued by the LVM layer. > For details, see [1] please. Ok, so you properly fixed the problem on the DM layer. > > After this problem was solved, we naturally checked other related log > IO paths, hoping that they would not be throttled by wbt_wait(), that > is, we hoped that they would be marked with REQ_SYNC | REQ_IDLE. > > For log recover IO, in the LVM scenario, we are not sure whether it > will be affected by IO on other LVs on the same PV. In addition, we > did not find any obvious side effects of this patch. An ounce of > prevention is worth a pound of cure, and we think it is more > appropriate to add REQ_IDLE here. If you notice any problem with this that you're trying to fix, or if this change improves anything, please specify that in the commit message - also addressing comments by Christoph, i.e. xfs_rw_bdev shouldn't be messing with request ops - Just because it has no side-effects is not a good reason. Regular Log IO being throttled by the DM layer is indeed a problem, but considering the very small amount of data written here during log recovery doesn't seem a good use of REQ_IDLE. So, for now, NAK. Carlos > > Of course, if there is really a reason not to consider being throttled, > please forgive me for disturbing you. > > [1] https://lore.kernel.org/linux-xfs/20250220112014.3209940-1-alexjlzheng@xxxxxxxxxxx/ > > Thank you very much. :) > Jinliang Zheng > > > > > -Dave. > > -- > > Dave Chinner > > david@xxxxxxxxxxxxx
