On Mon, Mar 08, 2021 at 06:34:58PM +0800, Kunkun Jiang wrote: > Hi, > > On 2021/3/5 22:22, Peter Xu wrote: > > Kunkun, > > > > On Fri, Mar 05, 2021 at 03:50:34PM +0800, Kunkun Jiang wrote: > > > When the host page is a huge page and something is sent in the > > > current iteration, the migration_rate_limit() should be executed. > > > If not, this function can be omitted to save time. > > > > > > Rename tmppages to pages_this_iteration to express its meaning > > > more clearly. > > > > > > Signed-off-by: Keqian Zhu <zhukeqi...@huawei.com> > > > Signed-off-by: Kunkun Jiang <jiangkun...@huawei.com> > > > --- > > > migration/ram.c | 21 ++++++++++++++------- > > > 1 file changed, 14 insertions(+), 7 deletions(-) > > > > > > diff --git a/migration/ram.c b/migration/ram.c > > > index a168da5cdd..9fc5b2997c 100644 > > > --- a/migration/ram.c > > > +++ b/migration/ram.c > > > @@ -1988,7 +1988,7 @@ static int ram_save_target_page(RAMState *rs, > > > PageSearchStatus *pss, > > > static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, > > > bool last_stage) > > > { > > > - int tmppages, pages = 0; > > > + int pages = 0; > > > size_t pagesize_bits = > > > qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; > > > unsigned long start_page = pss->page; > > > @@ -2000,21 +2000,28 @@ static int ram_save_host_page(RAMState *rs, > > > PageSearchStatus *pss, > > > } > > > do { > > > + int pages_this_iteration = 0; > > > + > > > /* Check if the page is dirty and send it if it is */ > > > if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { > > > pss->page++; > > > continue; > > > } > > > - tmppages = ram_save_target_page(rs, pss, last_stage); > > > - if (tmppages < 0) { > > > - return tmppages; > > > + pages_this_iteration = ram_save_target_page(rs, pss, last_stage); > > > + if (pages_this_iteration < 0) { > > > + return pages_this_iteration; > > > } > > > - pages += tmppages; > > > + pages += pages_this_iteration; > > To me, both names are okay, it's just that the new name doesn't really > > provide > > a lot more new information, while it's even longer... > > > > Since you seem to prefer cleaning up tmppages, I'm actually thinking whether > > it should be called as "pages" at all since ram_save_target_page() majorly > > only > > returns either 1 if succeeded or <0 if error. There's only one very corner > > case of xbzrle where it can return 0 in save_xbzrle_page(): > > > > if (encoded_len == 0) { > > trace_save_xbzrle_page_skipping(); > > return 0; > > } > > > > I think it means the page didn't change at all, then I'm also wondering > > maybe > > it can also return 1 showing one page migrated (though actually skipped!) > > which > > should still be fine for the callers, e.g., ram_find_and_save_block() who > > will > > finally check this "pages" value. > > > > So I think _maybe_ that's a nicer cleanup to change that "return 0" to > > "return > > 1", then another patch to make the return value to be (1) return 0 if page > > saved, or (2) return <0 if error. Then here in ram_save_host_page() > > tmppages > > can be renamed to "ret" or "succeed". > Thanks for your advice. > change "return 0" to "return 1" would have a slight effect on > 'rs->target_page_count += pages' > in ram_save_iterate(). This may lead to consider more complex situations. > What do you think of > this?
I don't think we should change the meaning of ram_save_host_page()'s return value, but only ram_save_target_page(); ram_save_host_page() could return >1 for huge pages. Thanks, -- Peter Xu