* Juan Quintela (quint...@redhat.com) wrote: > "Dr. David Alan Gilbert" <dgilb...@redhat.com> wrote: > > * Juan Quintela (quint...@redhat.com) wrote: > >> The function still don't use multifd, but we have simplified > >> ram_save_page, xbzrle and RDMA stuff is gone. We have added a new > >> counter and a new flag for this type of pages. > > > >> +static int ram_multifd_page(QEMUFile *f, PageSearchStatus *pss, > >> + bool last_stage, uint64_t *bytes_transferred) > >> +{ > >> + int pages; > >> + uint8_t *p; > >> + RAMBlock *block = pss->block; > >> + ram_addr_t offset = pss->offset; > >> + > >> + p = block->host + offset; > >> + > >> + if (block == last_sent_block) { > >> + offset |= RAM_SAVE_FLAG_CONTINUE; > >> + } > >> + pages = save_zero_page(f, block, offset, p, bytes_transferred); > >> + if (pages == -1) { > >> + *bytes_transferred += > >> + save_page_header(f, block, offset | > >> RAM_SAVE_FLAG_MULTIFD_PAGE); > >> + qemu_put_buffer(f, p, TARGET_PAGE_SIZE); > >> + *bytes_transferred += TARGET_PAGE_SIZE; > >> + pages = 1; > >> + acct_info.norm_pages++; > >> + acct_info.multifd_pages++; > >> + } > >> + > >> + return pages; > >> +} > >> + > >> static int do_compress_ram_page(QEMUFile *f, RAMBlock *block, > >> ram_addr_t offset) > >> { > >> @@ -1427,6 +1461,8 @@ static int ram_save_target_page(MigrationState *ms, > >> QEMUFile *f, > >> res = ram_save_compressed_page(f, pss, > >> last_stage, > >> bytes_transferred); > >> + } else if (migrate_use_multifd()) { > >> + res = ram_multifd_page(f, pss, last_stage, bytes_transferred); > > > > I'm curious whether it's best to pick the destination fd at this level or > > one level > > higher; for example would it be good to keep all the components of a > > host page or huge > > page together on the same fd? If so then it would be best to pick the fd > > at ram_save_host_page level. > > my plan here would be to change the migration code to be able to call > with a bigger sizes, not page by page, and then the problem is solved by > itself?
Yes it might be, but you may have to be careful to keep all your FDs busy; for example, imagine that we're using huge pages, and you try and stuff an entire hugepage down one FD, for 2MB hugepages that's about half of the write buffer (tcp-wmem?) so there's a fair chance it'll block. But thereagain I think it's probably the right thing to do as long as you can get different pages down different FDs. Dave > Later, Juan. > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK