| Message ID | 20210223021646.500-4-jiangkunkun@huawei.com |
|---|---|
| State | New |
| Headers | show |
| Series | migration/ram: Some modifications about ram_save_host_page() | expand |
On Tuesday, 2021-02-23 at 10:16:45 +08, Kunkun Jiang wrote: > Starting from pss->page, ram_save_host_page() will check every page > and send the dirty pages up to the end of the current host page or > the boundary of used_length of the block. If the host page size is > a huge page, the step "check" will take a lot of time. > > This will improve performance to use migration_bitmap_find_dirty(). > > Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com> > Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com> > --- > migration/ram.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/migration/ram.c b/migration/ram.c > index c7e18dc2fc..c7a2350198 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -1994,6 +1994,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, > int tmppages, pages = 0; > size_t pagesize_bits = > qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; > + unsigned long hostpage_boundary = > + QEMU_ALIGN_UP(pss->page + 1, pagesize_bits); > unsigned long start_page = pss->page; > int res; > > @@ -2005,8 +2007,7 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, > do { > /* Check the pages is dirty and if it is send it */ > if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { > - pss->page++; > - continue; > + goto find_next; > } > > tmppages = ram_save_target_page(rs, pss, last_stage); > @@ -2015,16 +2016,17 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, > } > > pages += tmppages; > - pss->page++; > /* Allow rate limiting to happen in the middle of huge pages */ > if (pagesize_bits > 1) { > migration_rate_limit(); > } > - } while ((pss->page & (pagesize_bits - 1)) && > +find_next: > + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page); > + } while ((pss->page < hostpage_boundary) && > offset_in_ramblock(pss->block, > ((ram_addr_t)pss->page) << TARGET_PAGE_BITS)); This ends up looking very messy, with a goto inside the loop. Wouldn't it be cleaner to invert the sense of the migration_bitmap_clear_dirty() test, such that migration_bitmap_find_dirty() is called after the body of the test? > - /* The offset we leave with is the last one we looked at */ > - pss->page--; > + /* The offset we leave with is the min boundary of host page and block */ > + pss->page = MIN(pss->page, hostpage_boundary) - 1; > > res = ram_save_release_protection(rs, pss, start_page); > return (res < 0 ? res : pages); > -- > 2.23.0 dme.
On 2021/2/25 20:48, David Edmondson wrote: > On Tuesday, 2021-02-23 at 10:16:45 +08, Kunkun Jiang wrote: > >> Starting from pss->page, ram_save_host_page() will check every page >> and send the dirty pages up to the end of the current host page or >> the boundary of used_length of the block. If the host page size is >> a huge page, the step "check" will take a lot of time. >> >> This will improve performance to use migration_bitmap_find_dirty(). >> >> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com> >> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com> >> --- >> migration/ram.c | 14 ++++++++------ >> 1 file changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/migration/ram.c b/migration/ram.c >> index c7e18dc2fc..c7a2350198 100644 >> --- a/migration/ram.c >> +++ b/migration/ram.c >> @@ -1994,6 +1994,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, >> int tmppages, pages = 0; >> size_t pagesize_bits = >> qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; >> + unsigned long hostpage_boundary = >> + QEMU_ALIGN_UP(pss->page + 1, pagesize_bits); >> unsigned long start_page = pss->page; >> int res; >> >> @@ -2005,8 +2007,7 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, >> do { >> /* Check the pages is dirty and if it is send it */ >> if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { >> - pss->page++; >> - continue; >> + goto find_next; >> } >> >> tmppages = ram_save_target_page(rs, pss, last_stage); >> @@ -2015,16 +2016,17 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, >> } >> >> pages += tmppages; >> - pss->page++; >> /* Allow rate limiting to happen in the middle of huge pages */ >> if (pagesize_bits > 1) { >> migration_rate_limit(); >> } >> - } while ((pss->page & (pagesize_bits - 1)) && >> +find_next: >> + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page); >> + } while ((pss->page < hostpage_boundary) && >> offset_in_ramblock(pss->block, >> ((ram_addr_t)pss->page) << TARGET_PAGE_BITS)); > This ends up looking very messy, with a goto inside the loop. > > Wouldn't it be cleaner to invert the sense of the > migration_bitmap_clear_dirty() test, such that > migration_bitmap_find_dirty() is called after the body of the test? Sorry for the late reply. Thanks for your advice. I will post a v2 as soon as possible. Best Regards. Kunkun Jiang >> - /* The offset we leave with is the last one we looked at */ >> - pss->page--; >> + /* The offset we leave with is the min boundary of host page and block */ >> + pss->page = MIN(pss->page, hostpage_boundary) - 1; >> >> res = ram_save_release_protection(rs, pss, start_page); >> return (res < 0 ? res : pages); >> -- >> 2.23.0 > dme.
diff --git a/migration/ram.c b/migration/ram.c index c7e18dc2fc..c7a2350198 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1994,6 +1994,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, int tmppages, pages = 0; size_t pagesize_bits = qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS; + unsigned long hostpage_boundary = + QEMU_ALIGN_UP(pss->page + 1, pagesize_bits); unsigned long start_page = pss->page; int res; @@ -2005,8 +2007,7 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, do { /* Check the pages is dirty and if it is send it */ if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { - pss->page++; - continue; + goto find_next; } tmppages = ram_save_target_page(rs, pss, last_stage); @@ -2015,16 +2016,17 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss, } pages += tmppages; - pss->page++; /* Allow rate limiting to happen in the middle of huge pages */ if (pagesize_bits > 1) { migration_rate_limit(); } - } while ((pss->page & (pagesize_bits - 1)) && +find_next: + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page); + } while ((pss->page < hostpage_boundary) && offset_in_ramblock(pss->block, ((ram_addr_t)pss->page) << TARGET_PAGE_BITS)); - /* The offset we leave with is the last one we looked at */ - pss->page--; + /* The offset we leave with is the min boundary of host page and block */ + pss->page = MIN(pss->page, hostpage_boundary) - 1; res = ram_save_release_protection(rs, pss, start_page); return (res < 0 ? res : pages);