On 4/11/22 7:52 PM, Vivek Goyal wrote: > On Mon, Apr 11, 2022 at 10:10:23AM +0800, JeffleXu wrote: >> >> >> On 4/8/22 8:06 PM, Vivek Goyal wrote: >>> On Fri, Apr 08, 2022 at 07:50:55PM +0800, JeffleXu wrote: >>>> >>>> >>>> On 4/8/22 7:25 PM, Vivek Goyal wrote: >>>>> On Fri, Apr 08, 2022 at 10:36:40AM +0800, JeffleXu wrote: >>>>>> >>>>>> >>>>>> On 4/7/22 10:10 PM, Vivek Goyal wrote: >>>>>>> On Sat, Apr 02, 2022 at 06:32:50PM +0800, Jeffle Xu wrote: >>>>>>>> Move dmap free worker kicker inside the critical region, so that extra >>>>>>>> spinlock lock/unlock could be avoided. >>>>>>>> >>>>>>>> Suggested-by: Liu Jiang <gerry@xxxxxxxxxxxxxxxxx> >>>>>>>> Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx> >>>>>>> >>>>>>> Looks good to me. Have you done any testing to make sure nothing is >>>>>>> broken. >>>>>> >>>>>> xfstests -g quick shows no regression. The tested virtiofs is mounted >>>>>> with "dax=always". >>>>> >>>>> I think xfstests might not trigger reclaim. You probably will have to >>>>> run something like blogbench with a small dax window like 1G so that >>>>> heavy reclaim happens. >>>> >>>> >>>> Actually, I configured the DAX window to 8MB, i.e. 4 slots when running >>>> xfstests. Thus I think the reclaim path is most likely triggered. >>>> >>>> >>>>> >>>>> For fun, I sometimes used to run it with a window of just say 16 dax >>>>> ranges so that reclaim was so heavy that if there was a bug, it will >>>>> show up. >>>>> >>>> >>>> Yeah, my colleague had ever reported that a DAX window of 4KB will cause >>>> hang in our internal OS (which is 4.19, we back ported virtiofs to >>>> 4.19). But then I found that this issue doesn't exist in the latest >>>> upstream. The reason seems that in the upstream kernel, >>>> devm_memremap_pages() called in virtio_fs_setup_dax() will fail directly >>>> since the dax window (4KB) is not aligned with the sparse memory section. >>> >>> Given our default chunk size is 2MB (FUSE_DAX_SHIFT), may be it is not >>> a bad idea to enforce some minimum cache window size. IIRC, even one >>> range is not enough. Minimum 2 are required for reclaim to not deadlock. >> >> Curiously, why minimum 1 range is not adequate? In which case minimum 2 >> are required? > > Frankly speaking, right now I don't remember. I have vague memories > of concluding in the past that 1 range is not sufficient. But if you > like dive deeper, and try with one range and see if you can introduce > deadlock. > Alright, thanks. -- Thanks, Jeffle
