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From: | Kunkun Jiang |
Subject: | Re: [PATCH v2 3/3] migration/ram: Optimize ram_save_host_page() |
Date: | Wed, 3 Mar 2021 19:47:20 +0800 |
User-agent: | Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 |
On 2021/3/3 16:56, David Edmondson wrote:
On Monday, 2021-03-01 at 16:21:32 +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().This is cleaner, thank you. I was hoping to just invert the body of the loop - something like (completely untested):
Sorry for my misunderstanding. I will improve it in the next version.
do { int pages_this_iteration = 0; /* Check if the page is dirty and, if so, send it. */ if (migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { pages_this_iteration = ram_save_target_page(rs, pss, last_stage); if (pages_this_iteration < 0) { return pages_this_iteration; } pages += pages_this_iteration; /* * Allow rate limiting to happen in the middle of huge pages if * the current iteration sent something. */ if (pagesize_bits > 1 && pages_this_iteration > 0) { migration_rate_limit(); }
I missed the case that the value of pages_this_iteration is 0. 😅
} 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 min boundary of host page and block */ pss->page = MIN(pss->page, hostpage_boundary) - 1;
Best Regards. Kunkun Jiang
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com> --- migration/ram.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index 3a9115b6dc..a1374db356 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1991,6 +1991,8 @@ 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;@@ -2002,7 +2004,7 @@ 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++; + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page); continue; }@@ -2012,16 +2014,16 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,}pages += tmppages;- pss->page++; + pss->page = migration_bitmap_find_dirty(rs, pss->block, 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)) && + } 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); -- 2.23.0dme.
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