From ae1a8506aa45266f2bf77a8d428f5ccd970a9b13 Mon Sep 17 00:00:00 2001 From: Kunkun Jiang Date: Tue, 16 Mar 2021 20:57:16 +0800 Subject: [PATCH] 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 Signed-off-by: Kunkun Jiang Reviewed-by: Peter Xu Message-Id: <20210316125716.1243-3-jiangkunkun@huawei.com> Signed-off-by: Dr. David Alan Gilbert --- migration/ram.c | 43 +++++++++++++++++++++---------------------- 1 file changed, 21 insertions(+), 22 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index 22063e00b4..1bd99ff9e5 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -3052,6 +3052,8 @@ 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); if (ramblock_is_ignored(pss->block)) { error_report("block %s should not be migrated !", pss->block->idstr); @@ -3060,34 +3062,31 @@ 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; - if (pss->block->unsentmap) { - clear_bit(pss->page, pss->block->unsentmap); - } + pages += tmppages; + if (pss->block->unsentmap) { + clear_bit(pss->page, pss->block->unsentmap); + } - 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(); + /* + * 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(); + } } + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page); } while ((pss->page & (pagesize_bits - 1)) && offset_in_ramblock(pss->block, 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; return pages; } -- 2.27.0