On Wed, Aug 12, 2020 at 5:48 AM Yufen Yu <yuyufen@xxxxxxxxxx> wrote: > > Hi, all > > In current implementation, grow_buffers() uses alloc_page() to allocate > the buffers for each stripe_head, i.e. allocate a page for each dev[i] > in stripe_head. > > After setting stripe_size as a configurable value by writing sysfs entry, > it means that we always allocate 64K buffers, but just use 4K of them when > stripe_size is 4K in 64KB arm64. > > To save memory, we try to let multiple buffers of stripe_head to share only > one real page when page size is bigger than stripe_size. Detail can be > seen in patch #10. > > This patch set is subsequent optimization for configurable stripe_size, > which based on the origin patches[1] but reorganized them. > > Patch 1 ~ 2 try to replace current page offset '0' with dev[i].offset. > Patch 3 ~ 5 let xor compute functions support different page offset for raid5. > Patch 6 ~ 9 let syndrome and recovery function support different page offset for raid6. > All of these patch are preparing for shared page. There is no functional change. > > Patch 10 ~ 11 actually implement shared page between multiple devices of > stripe_head. But they only make sense for PAGE_SIZE != 4096, likely, 64KB arm64 > system. It doesn't make any difference for PAGE_SIZE == 4096 system, likely x86. Thanks for the patches. I went through the first half of the set, most of the code looks fine. However, there is one issue: the way you split the changes into 12 patches is not ideal. The most significant issue is that build failed after 5/12 or 6/12 (and was fixed after 9/12). We would like every commit build successfully. I think the proper fix is to break 9/12 and merge changes in raid5.c to proper patches. Also, I think we can merge 1/12 and 2/12. Please resubmit after these changes. Thanks, Song
