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author | Kunkun Jiang <jiangkunkun@huawei.com> | 2021-03-16 20:57:16 +0800 |
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committer | Dr. David Alan Gilbert <dgilbert@redhat.com> | 2021-05-13 18:21:13 +0100 |
commit | ba1b7c812c1efa49f9c297b6a22c598ff0eb5a4b (patch) | |
tree | 2e2af203529ac74af5ca61cf7425943441b49cc2 | |
parent | 23feba906e42747463aa233fb54c58d7f02430c9 (diff) | |
download | qemu-ba1b7c812c1efa49f9c297b6a22c598ff0eb5a4b.zip qemu-ba1b7c812c1efa49f9c297b6a22c598ff0eb5a4b.tar.gz qemu-ba1b7c812c1efa49f9c297b6a22c598ff0eb5a4b.tar.bz2 |
migration/ram: Optimize ram_save_host_page()
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.
It will improve performance to use migration_bitmap_find_dirty().
Tested on Kunpeng 920; VM parameters: 1U 4G (page size 1G)
The time of ram_save_host_page() in the last round of ram saving:
before optimize: 9250us after optimize: 34us
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210316125716.1243-3-jiangkunkun@huawei.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
-rw-r--r-- | migration/ram.c | 39 |
1 files changed, 19 insertions, 20 deletions
diff --git a/migration/ram.c b/migration/ram.c index 00b579b..bb52bd9 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -2013,6 +2013,8 @@ 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; @@ -2023,30 +2025,27 @@ 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; - } - - tmppages = ram_save_target_page(rs, pss, last_stage); - if (tmppages < 0) { - return tmppages; - } + if (migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { + tmppages = ram_save_target_page(rs, pss, last_stage); + if (tmppages < 0) { + return tmppages; + } - pages += tmppages; - pss->page++; - /* - * Allow rate limiting to happen in the middle of huge pages if - * something is sent in the current iteration. - */ - if (pagesize_bits > 1 && tmppages > 0) { - migration_rate_limit(); + pages += tmppages; + /* + * Allow rate limiting to happen in the middle of huge pages if + * something is sent in the current iteration. + */ + if (pagesize_bits > 1 && tmppages > 0) { + migration_rate_limit(); + } } - } while ((pss->page & (pagesize_bits - 1)) && + 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); |