Avoid the hot pages cache replacing by others to remarkable decrease cache
missing. The counter of updating dirty bitmap is used to indicate the cached
page age.
Signed-off-by: ChenLiang <chenlian...@huawei.com>
Signed-off-by: Gonglei <arei.gong...@huawei.com>
---
arch_init.c | 8 +++++---
include/migration/page_cache.h | 8 ++++++--
page_cache.c | 19 +++++++++++++++----
3 files changed, 26 insertions(+), 9 deletions(-)
diff --git a/arch_init.c b/arch_init.c
index 6823c5a..fc71331 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -315,7 +315,8 @@ static void xbzrle_cache_zero_page(ram_addr_t current_addr)
/* We don't care if this fails to allocate a new cache page
* as long as it updated an old one */
- cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE);
+ cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE,
+ get_bitmap_sync_cnt());
}
#define ENCODING_FLAG_XBZRLE 0x1
@@ -327,10 +328,11 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t
**current_data,
int encoded_len = 0, bytes_sent = -1;
uint8_t *prev_cached_page;
- if (!cache_is_cached(XBZRLE.cache, current_addr)) {
+ if (!cache_is_cached(XBZRLE.cache, current_addr, get_bitmap_sync_cnt())) {
acct_info.xbzrle_cache_miss++;
if (!last_stage) {
- if (cache_insert(XBZRLE.cache, current_addr, *current_data) == -1)
{
+ if (cache_insert(XBZRLE.cache, current_addr, *current_data,
+ get_bitmap_sync_cnt()) == -1) {
return -1;
} else {
/* update *current_data when the page has been
diff --git a/include/migration/page_cache.h b/include/migration/page_cache.h
index 2d5ce2d..cadce55 100644
--- a/include/migration/page_cache.h
+++ b/include/migration/page_cache.h
@@ -43,8 +43,10 @@ void cache_fini(PageCache *cache);
*
* @cache pointer to the PageCache struct
* @addr: page addr
+ * @current_age indicate age of the page if cache hit
*/
-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
@@ -65,8 +67,10 @@ uint8_t *get_cached_data(const PageCache *cache, uint64_t
addr);
* @cache pointer to the PageCache struct
* @addr: page address
* @pdata: pointer to the page
+ * @current_age indicate age of the page if the page is inserted into cache
*/
-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
diff --git a/page_cache.c b/page_cache.c
index b033681..fa58ab2 100644
--- a/page_cache.c
+++ b/page_cache.c
@@ -121,7 +121,8 @@ static size_t cache_get_cache_pos(const PageCache *cache,
return pos;
}
-bool cache_is_cached(const PageCache *cache, uint64_t addr)
+bool cache_is_cached(const PageCache *cache, uint64_t addr,
+ uint64_t current_age)
{
size_t pos;
@@ -130,7 +131,12 @@ bool cache_is_cached(const PageCache *cache, uint64_t addr)
pos = cache_get_cache_pos(cache, addr);
- return (cache->page_cache[pos].it_addr == addr);
+ if (cache->page_cache[pos].it_addr == addr) {
+ /* updata the it_age when the cache hit */
+ cache->page_cache[pos].it_age = current_age;
+ return true;
+ }
+ return false;
}
static CacheItem *cache_get_by_addr(const PageCache *cache, uint64_t addr)
@@ -150,7 +156,8 @@ uint8_t *get_cached_data(const PageCache *cache, uint64_t
addr)
return cache_get_by_addr(cache, addr)->it_data;
}
-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)
{
CacheItem *it = NULL;
@@ -161,6 +168,10 @@ int cache_insert(PageCache *cache, uint64_t addr, const
uint8_t *pdata)
/* actual update of entry */
it = cache_get_by_addr(cache, addr);
+ if ((it->it_data != NULL) && (it->it_age + 2 > current_age)) {
+ /* the cache page is fresh, don't replace it */
+ return -1;
+ }
/* allocate page */
if (!it->it_data) {
it->it_data = g_try_malloc(cache->page_size);
@@ -173,7 +184,7 @@ int cache_insert(PageCache *cache, uint64_t addr, const
uint8_t *pdata)
memcpy(it->it_data, pdata, cache->page_size);
- it->it_age = ++cache->max_item_age;
+ it->it_age = current_age;
it->it_addr = addr;
return 0;
--
1.7.12.4
Best regards,
-Gonglei
