aboutsummaryrefslogtreecommitdiff
path: root/block/qcow2-cache.c
diff options
context:
space:
mode:
authorAlberto Garcia <berto@igalia.com>2015-08-04 15:14:40 +0300
committerMax Reitz <mreitz@redhat.com>2015-09-04 21:00:32 +0200
commit279621c046ce57de0af9e3c00663b48d3a7835ae (patch)
treee14d8ab78e7bfcddf42b763a120cc8d116d38430 /block/qcow2-cache.c
parent355ee2d0e8ca536a6278c9c763ddd2f136eace3f (diff)
downloadqemu-279621c046ce57de0af9e3c00663b48d3a7835ae.zip
qemu-279621c046ce57de0af9e3c00663b48d3a7835ae.tar.gz
qemu-279621c046ce57de0af9e3c00663b48d3a7835ae.tar.bz2
qcow2: add option to clean unused cache entries after some time
This adds a new 'cache-clean-interval' option that cleans all qcow2 cache entries that haven't been used in a certain interval, given in seconds. This allows setting a large L2 cache size so it can handle scenarios with lots of I/O and at the same time use little memory during periods of inactivity. This feature currently relies on MADV_DONTNEED to free that memory, so it is not useful in systems that don't follow that behavior. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: a70d12da60433df9360ada648b3f34b8f6f354ce.1438690126.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'block/qcow2-cache.c')
-rw-r--r--block/qcow2-cache.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c
index f63e7d8..8457458 100644
--- a/block/qcow2-cache.c
+++ b/block/qcow2-cache.c
@@ -49,6 +49,7 @@ struct Qcow2Cache {
bool depends_on_flush;
void *table_array;
uint64_t lru_counter;
+ uint64_t cache_clean_lru_counter;
};
static inline void *qcow2_cache_get_table_addr(BlockDriverState *bs,
@@ -84,6 +85,40 @@ static void qcow2_cache_table_release(BlockDriverState *bs, Qcow2Cache *c,
#endif
}
+static inline bool can_clean_entry(Qcow2Cache *c, int i)
+{
+ Qcow2CachedTable *t = &c->entries[i];
+ return t->ref == 0 && !t->dirty && t->offset != 0 &&
+ t->lru_counter <= c->cache_clean_lru_counter;
+}
+
+void qcow2_cache_clean_unused(BlockDriverState *bs, Qcow2Cache *c)
+{
+ int i = 0;
+ while (i < c->size) {
+ int to_clean = 0;
+
+ /* Skip the entries that we don't need to clean */
+ while (i < c->size && !can_clean_entry(c, i)) {
+ i++;
+ }
+
+ /* And count how many we can clean in a row */
+ while (i < c->size && can_clean_entry(c, i)) {
+ c->entries[i].offset = 0;
+ c->entries[i].lru_counter = 0;
+ i++;
+ to_clean++;
+ }
+
+ if (to_clean > 0) {
+ qcow2_cache_table_release(bs, c, i - to_clean, to_clean);
+ }
+ }
+
+ c->cache_clean_lru_counter = c->lru_counter;
+}
+
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables)
{
BDRVQcowState *s = bs->opaque;