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? -- Thanks, Jeffle
