Hao Xiang <hao.xi...@bytedance.com> writes: > On Wed, Jan 31, 2024 at 5:19 AM Fabiano Rosas <faro...@suse.de> wrote: >> >> Peter Xu <pet...@redhat.com> writes: >> >> > On Mon, Jan 29, 2024 at 09:51:06AM -0300, Fabiano Rosas wrote: >> >> Peter Xu <pet...@redhat.com> writes: >> >> >> >> > On Mon, Jan 29, 2024 at 01:41:01AM +0000, Liu, Yuan1 wrote: >> >> >> Because this change has an impact on the previous live migration >> >> >> With IAA Patch, does the submission of the next version needs >> >> >> to be submitted based on this change? >> >> > >> >> > I'd say hold off a little while until we're more certain on the planned >> >> > interface changes, to avoid you rebase your code back and forth; unless >> >> > you're pretty confident that this will be the right approach. >> >> > >> >> > I apologize on not having looked at any of the QAT/IAA compression / >> >> > zero >> >> > detection series posted on the list; I do plan to read them very soon >> >> > too >> >> > after Fabiano. So I may not have a complete full picture here yet, >> >> > please >> >> > bare with me. >> >> > >> >> > If this series is trying to provide a base ground for all the efforts, >> >> > it'll be great if we can thoroughly discuss here and settle an approach >> >> > soon that will satisfy everyone. >> >> >> >> Just a summary if it helps: >> >> >> >> For compression work (IAA/QPL, QAT) the discussion is around having a >> >> new "compression acceleration" option that enables the accelerators and >> >> is complementary to the existing zlib compression method. We'd choose >> >> those automatically based on availability and we'd make HW accelerated >> >> compression produce a stream that is compatible with QEMU's zlib stream >> >> so we could migrate between solutions. >> >> >> >> For zero page work and zero page acceleration (DSA), the question is how >> >> to fit zero page detection into multifd and whether we need a new hook >> >> multifd_ops->zero_page_detect() (or similar) to allow client code to >> >> provide it's own zero page detection methods. My worry here is that >> >> teaching multifd to recognize zero pages is one more coupling to the >> >> "pages" data type. Ideallly we'd find a way to include that operation as >> >> a prepare() responsibility and the client code would deal with it. >> > >> > Thanks Fabiano. > > Hi Fabiano, > > Your current refactoring assumes that compression ops and multifd > socket ops are mutually exclusive. Both of them need to implement the > entire MultiFDMethods interface. I think this works fine for now. Once > we introduce multifd zero page checking and we add a new interface for > that, we are adding a new method zero_page_detect() on the > MultiFDMethods interface. If we do that, zero_page_detect() needs to > be implemented in multifd_socket_ops and it also needs to be > implemented in zlib and zstd. On top of that, if we add an accelerator > to offload zero_page_detect(), that accelerator configuration can > co-exist with compression or socket. That makes things quite > complicated in my opinion.
Peter has proposed an alternate scheme. Take a look at his series. But it basically keeps the compression as is and moves some code into the prepare() phase: https://lore.kernel.org/r/20240131103111.306523-1-pet...@redhat.com > Can we create an instance of MultiFDMethods at runtime and fill each > method depending on the configuration? If methods are not filled, we > fallback to fill it with the default implementation (like what > socket.c provides) For instance, if zstd is enabled and zero page > checking using CPU, the interface will be filled with all the > functions zstd currently implements and since zstd doesn't implement > zero_page_detect(), we will fallback to fill zero_page_detect() with > the default multifd zero page checking implementation. Take a look whether incorporating zero_page_detect() in the prepare() phase would work. We're trying to walk toward a multifd_ops model that is not tied to the pages concept. >> > >> > Since I'm preparing the old series to post for some fundamental cleanups >> > around multifd, and when I'm looking around the code, I noticed that >> > _maybe_ it'll also be eaiser to apply such a series if we can cleanup more >> > things then move towards a clean base to add more accelerators. >> > >> > I agree many ideas in your this series, but I may address it slightly >> > different (e.g., I want to avoid send(), but you can consider that in the >> > fixed-ram series instead), also it'll be after some other cleanup I plan to >> > give a stab at which is not yet covered in this series. I hope I can add >> > your "Co-developed-by" in some of the patches there. If you haven't spend >> > more time on new version of this series, please wait 1-2 days so I can post >> > my thoughts. >> >> Sure, go ahead. >>
