motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-04 00:03:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

xbzrle: optimize XBZRLE to decrease the cache misses

Browse source 
Avoid hot pages being replaced by others to remarkably decrease cache
misses

Sample results with the test program which quote from xbzrle.txt ran in
vm:(migrate bandwidth:1GE and xbzrle cache size 8MB)

the test program:

include <stdlib.h>
include <stdio.h>
int main()
 {
        char *buf = (char *) calloc(4096, 4096);
        while (1) {
            int i;
            for (i = 0; i < 4096 * 4; i++) {
                buf[i * 4096 / 4]++;
            }
            printf(".");
        }
 }

before this patch:
virsh qemu-monitor-command test_vm '{"execute": "query-migrate"}'
{"return":{"expected-downtime":1020,"xbzrle-cache":{"bytes":1108284,
"cache-size":8388608,"cache-miss-rate":0.987013,"pages":18297,"overflow":8,
"cache-miss":1228737},"status":"active","setup-time":10,"total-time":52398,
"ram":{"total":12466991104,"remaining":1695744,"mbps":935.559472,
"transferred":5780760580,"dirty-sync-counter":271,"duplicate":2878530,
"dirty-pages-rate":29130,"skipped":0,"normal-bytes":5748592640,
"normal":1403465}},"id":"libvirt-706"}

18k pages sent compressed in 52 seconds.
cache-miss-rate is 98.7%, totally miss.

after optimizing:
virsh qemu-monitor-command test_vm '{"execute": "query-migrate"}'
{"return":{"expected-downtime":2054,"xbzrle-cache":{"bytes":5066763,
"cache-size":8388608,"cache-miss-rate":0.485924,"pages":194823,"overflow":0,
"cache-miss":210653},"status":"active","setup-time":11,"total-time":18729,
"ram":{"total":12466991104,"remaining":3895296,"mbps":937.663549,
"transferred":1615042219,"dirty-sync-counter":98,"duplicate":2869840,
"dirty-pages-rate":58781,"skipped":0,"normal-bytes":1588404224,
"normal":387794}},"id":"libvirt-266"}

194k pages sent compressed in 18 seconds.
The value of cache-miss-rate decrease to 48.59%.

Signed-off-by: ChenLiang <chenliang88@huawei.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
This commit is contained in:
ChenLiang 2014-11-24 19:55:47 +08:00 • committed by Amit Shah
parent df58887b20
commit 27af7d6ea5
4 changed files with 39 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

10
include/migration/page_cache.h
View file

@ -43,8 +43,10 @@ void cache_fini(PageCache *cache);
*
* @cache pointer to the PageCache struct
* @addr: page addr
* @current_age: current bitmap generation
*/
bool cache_is_cached(const PageCache *cache, uint64_t addr);
bool cache_is_cached(const PageCache *cache, uint64_t addr,
uint64_t current_age);
/**
* get_cached_data: Get the data cached for an addr
@ -60,13 +62,15 @@ uint8_t *get_cached_data(const PageCache *cache, uint64_t addr);
* cache_insert: insert the page into the cache. the page cache
* will dup the data on insert. the previous value will be overwritten
*
* Returns -1 on error
* Returns -1 when the page isn't inserted into cache
*
* @cache pointer to the PageCache struct
* @addr: page address
* @pdata: pointer to the page
* @current_age: current bitmap generation
*/
int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata);
int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
uint64_t current_age);
/**
* cache_resize: resize the page cache. In case of size reduction the extra