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27af7d6ea5
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>
87 lines
2.2 KiB
C
87 lines
2.2 KiB
C
/*
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* Page cache for QEMU
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* The cache is base on a hash of the page address
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*
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* Copyright 2012 Red Hat, Inc. and/or its affiliates
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*
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* Authors:
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* Orit Wasserman <owasserm@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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#ifndef PAGE_CACHE_H
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#define PAGE_CACHE_H
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/* Page cache for storing guest pages */
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typedef struct PageCache PageCache;
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/**
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* cache_init: Initialize the page cache
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*
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*
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* Returns new allocated cache or NULL on error
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*
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* @cache pointer to the PageCache struct
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* @num_pages: cache maximal number of cached pages
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* @page_size: cache page size
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*/
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PageCache *cache_init(int64_t num_pages, unsigned int page_size);
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/**
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* cache_fini: free all cache resources
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* @cache pointer to the PageCache struct
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*/
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void cache_fini(PageCache *cache);
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/**
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* cache_is_cached: Checks to see if the page is cached
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*
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* Returns %true if page is cached
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*
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* @cache pointer to the PageCache struct
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* @addr: page addr
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* @current_age: current bitmap generation
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*/
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bool cache_is_cached(const PageCache *cache, uint64_t addr,
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uint64_t current_age);
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/**
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* get_cached_data: Get the data cached for an addr
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*
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* Returns pointer to the data cached or NULL if not cached
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*
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* @cache pointer to the PageCache struct
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* @addr: page addr
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*/
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uint8_t *get_cached_data(const PageCache *cache, uint64_t addr);
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/**
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* cache_insert: insert the page into the cache. the page cache
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* will dup the data on insert. the previous value will be overwritten
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*
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* Returns -1 when the page isn't inserted into cache
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*
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* @cache pointer to the PageCache struct
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* @addr: page address
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* @pdata: pointer to the page
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* @current_age: current bitmap generation
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*/
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int cache_insert(PageCache *cache, uint64_t addr, const uint8_t *pdata,
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uint64_t current_age);
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/**
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* cache_resize: resize the page cache. In case of size reduction the extra
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* pages will be freed
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*
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* Returns -1 on error new cache size on success
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*
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* @cache pointer to the PageCache struct
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* @num_pages: new page cache size (in pages)
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*/
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int64_t cache_resize(PageCache *cache, int64_t num_pages);
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#endif
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