Hi, On Fri, Apr 21, 2023 at 10:19 PM Hillf Danton <hdanton@xxxxxxxx> wrote: > > On 21 Apr 2023 15:12:45 -0700 Douglas Anderson <dianders@xxxxxxxxxxxx> > > Add a variant of folio_lock() that can timeout. This is useful to > > avoid unbounded waits for the page lock in kcompactd. > > Given no mutex_lock_timeout() (perhaps because timeout makes no sense for > spinlock), I suspect your fix lies in the right layer. I'm not 100% sure I understood the above comment, but I think you're saying that the approach my patch takes seems OK. > If waiting for > page under IO causes trouble for you, another simpler option is make > IO faster (perhaps all you can do) for instance. Yeah, this gets into the discussion about whether our current squashfs settings actually make sense. I suspect that they don't and that we should look into EROFS like Gao suggested, or at least choose different squashfs settings (smaller block sizes, ZSTD instead of zlib). Unfortunately I believe that the current squashfs settings were chosen because disk space is a concern. > If kcompactd is waken > up by kswapd, waiting for slow IO is the right thing to do. I don't have enough intuition here, so I'm happy to take others' advice here. I guess my thought was that kcompactd is explicitly not using the full "sync" and instead choosing the "sync light". To me that means we shouldn't block for _too_ long. -Doug
