On Fri, May 18, 2018 at 1:12 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > On Fri, 18 May 2018, Dan Williams wrote: > >> On Fri, May 18, 2018 at 8:44 AM, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: >> > On Thu, Mar 08 2018 at 12:08pm -0500, >> > Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >> > >> >> Mikulas sent this useful enhancement to the memcpy_flushcache API: >> >> >> >> https://patchwork.kernel.org/patch/10217655/ >> >> >> >> ...it's in my queue to either push through -tip or add it to the next >> >> libnvdimm pull request for 4.17-rc1. >> > >> > Hi Dan, >> > >> > Seems this never actually went upstream. I've staged it in >> > linux-dm.git's "for-next" for the time being: >> > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.18&id=a7e96990b5ff6206fefdc5bfe74396bb880f7e48 >> > >> > But do you intend to pick it up for 4.18 inclusion? If so I'll drop >> > it.. would just hate for it to get dropped on the floor by getting lost >> > in the shuffle between trees. >> > >> > Please avise, thanks! >> > Mike >> >> Thanks for picking it up! I was hoping to resend it to get acks from >> x86 folks, and then yes it fell through the cracks in my patch >> tracking. >> >> Now that I look at it again I don't think we need this hunk: >> >> void memcpy_page_flushcache(char *to, struct page *page, size_t offset, >> size_t len) >> { >> char *from = kmap_atomic(page); >> - memcpy_flushcache(to, from + offset, len); >> + __memcpy_flushcache(to, from + offset, len); >> kunmap_atomic(from); >> } > > Yes - this is not needed. > >> ...and I wonder what the benefit is of the 16-byte case? I would >> assume the bulk of the benefit is limited to the 4 and 8 byte copy >> cases. > > dm-writecache uses 16-byte writes frequently, so it is needed for that. > > If we split 16-byte write to two 8-byte writes, it would degrade > performance for architectures where memcpy_flushcache needs to flush the > cache. My question was how measurable it is to special case 16-byte transfers? I know Ingo is going to ask this question, so it would speed things along if this patch included performance benefit numbers for each special case in the changelog. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
