packages/qemu
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

migration/ram: Optimize ram_save_host_page()

Browse Source 
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>
This commit is contained in:
Chen Qun 2021-03-16 20:57:16 +08:00
parent c9d492032d
commit 8c2655d625
1 changed files with 95 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

95
migration-ram-Optimize-ram_save_host_page.patch Normal file
View File

@ -0,0 +1,95 @@
From ae1a8506aa45266f2bf77a8d428f5ccd970a9b13 Mon Sep 17 00:00:00 2001
From: Kunkun Jiang <jiangkunkun@huawei.com>
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 <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>
---
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