On Wed, Feb 21, 2024 at 1:06 PM Fabiano Rosas <faro...@suse.de> wrote: > > Hao Xiang <hao.xi...@bytedance.com> writes: > > > This change adds a dedicated handler for MigrationOps::ram_save_target_page > > in > > nit: Add a dedicated handler... > > Usually "this patch/change" is used only when necessary to avoid > ambiguity.
Will do. > > > multifd live migration. Now zero page checking can be done in the multifd > > threads > > and this becomes the default configuration. We still provide backward > > compatibility > > where zero page checking is done from the migration main thread. > > > > Signed-off-by: Hao Xiang <hao.xi...@bytedance.com> > > --- > > migration/multifd.c | 1 + > > migration/options.c | 2 +- > > migration/ram.c | 53 ++++++++++++++++++++++++++++++++++----------- > > 3 files changed, 42 insertions(+), 14 deletions(-) > > > > diff --git a/migration/multifd.c b/migration/multifd.c > > index fbb40ea10b..ef5dad1019 100644 > > --- a/migration/multifd.c > > +++ b/migration/multifd.c > > @@ -13,6 +13,7 @@ > > #include "qemu/osdep.h" > > #include "qemu/cutils.h" > > This include... > > > #include "qemu/rcu.h" > > +#include "qemu/cutils.h" > > is there already. > > > #include "exec/target_page.h" > > #include "sysemu/sysemu.h" > > #include "exec/ramblock.h" > > diff --git a/migration/options.c b/migration/options.c > > index 3c603391b0..3c79b6ccd4 100644 > > --- a/migration/options.c > > +++ b/migration/options.c > > @@ -181,7 +181,7 @@ Property migration_properties[] = { > > MIG_MODE_NORMAL), > > DEFINE_PROP_ZERO_PAGE_DETECTION("zero-page-detection", MigrationState, > > parameters.zero_page_detection, > > - ZERO_PAGE_DETECTION_LEGACY), > > + ZERO_PAGE_DETECTION_MULTIFD), > > I think we'll need something to avoid a 9.0 -> 8.2 migration with this > enabled. Otherwise it will go along happily until we get data corruption > because the new QEMU didn't send any zero pages on the migration thread > and the old QEMU did not look for them in the multifd packet. > > Perhaps bumping the MULTIFD_VERSION when ZERO_PAGE_DETECTION_MULTIFD is > in use. We'd just need to fix the test in the new QEMU to check > (msg.version > MULTIFD_VERSION) instead of (msg.version != MULTIFD_VERSION). > > > > > /* Migration capabilities */ > > DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE), > > diff --git a/migration/ram.c b/migration/ram.c > > index 5ece9f042e..b088c5a98c 100644 > > --- a/migration/ram.c > > +++ b/migration/ram.c > > @@ -1123,10 +1123,6 @@ static int save_zero_page(RAMState *rs, > > PageSearchStatus *pss, > > QEMUFile *file = pss->pss_channel; > > int len = 0; > > > > - if (migrate_zero_page_detection() != ZERO_PAGE_DETECTION_LEGACY) { > > - return 0; > > - } > > How does 'none' work now? I tested it and all pages are transferred with payload (including the zero pages). > > > - > > if (!buffer_is_zero(p, TARGET_PAGE_SIZE)) { > > return 0; > > } > > @@ -1256,6 +1252,10 @@ static int ram_save_page(RAMState *rs, > > PageSearchStatus *pss) > > > > static int ram_save_multifd_page(RAMBlock *block, ram_addr_t offset) > > { > > + assert(migrate_multifd()); > > + assert(!migrate_compress()); > > + assert(!migration_in_postcopy()); > > Drop these, please. Keep only the asserts that are likely to trigger > during development, such as the existing ones at multifd_send_pages. I think I have got enough feedback regarding too many asserts. I will drop these. assert is not compiled into the free build, correct? > > > + > > if (!multifd_queue_page(block, offset)) { > > return -1; > > } > > @@ -2046,7 +2046,6 @@ static bool save_compress_page(RAMState *rs, > > PageSearchStatus *pss, > > */ > > static int ram_save_target_page_legacy(RAMState *rs, PageSearchStatus *pss) > > { > > - RAMBlock *block = pss->block; > > ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS; > > int res; > > > > @@ -2062,17 +2061,40 @@ static int ram_save_target_page_legacy(RAMState > > *rs, PageSearchStatus *pss) > > return 1; > > } > > > > + return ram_save_page(rs, pss); > > Look at where git put this! Are you using the default diff algorithm? If > not try using --patience to see if it improves the diff. I used the default diff algorithm. > > > +} > > + > > +/** > > + * ram_save_target_page_multifd: save one target page > > + * > > + * Returns the number of pages written > > We could be more precise here: > > ram_save_target_page_multifd: send one target page to multifd workers > > Returns 1 if the page was queued, -1 otherwise. Will do. > > > + * > > + * @rs: current RAM state > > + * @pss: data about the page we want to send > > + */ > > +static int ram_save_target_page_multifd(RAMState *rs, PageSearchStatus > > *pss) > > +{ > > + RAMBlock *block = pss->block; > > + ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS; > > + > > + /* Multifd is not compatible with old compression. */ > > + assert(!migrate_compress()); > > This should already be enforced at options.c. > > > + > > + /* Multifd is not compabible with postcopy. */ > > + assert(!migration_in_postcopy()); > > Same here. > > > + > > /* > > - * Do not use multifd in postcopy as one whole host page should be > > - * placed. Meanwhile postcopy requires atomic update of pages, so even > > - * if host page size == guest page size the dest guest during run may > > - * still see partially copied pages which is data corruption. > > + * Backward compatibility support. While using multifd live > > + * migration, we still need to handle zero page checking on the > > + * migration main thread. > > */ > > - if (migrate_multifd() && !migration_in_postcopy()) { > > - return ram_save_multifd_page(block, offset); > > + if (migrate_zero_page_detection() == ZERO_PAGE_DETECTION_LEGACY) { > > + if (save_zero_page(rs, pss, offset)) { > > + return 1; > > + } > > } > > > > - return ram_save_page(rs, pss); > > + return ram_save_multifd_page(block, offset); > > } > > > > /* Should be called before sending a host page */ > > @@ -2984,7 +3006,12 @@ static int ram_save_setup(QEMUFile *f, void *opaque) > > } > > > > migration_ops = g_malloc0(sizeof(MigrationOps)); > > - migration_ops->ram_save_target_page = ram_save_target_page_legacy; > > + > > + if (migrate_multifd()) { > > + migration_ops->ram_save_target_page = ram_save_target_page_multifd; > > + } else { > > + migration_ops->ram_save_target_page = ram_save_target_page_legacy; > > + } > > > > bql_unlock(); > > ret = multifd_send_sync_main();