* THE SOFTWARE.
*/
-#include "block/block_int.h"
-#include "qemu-common.h"
+#include "qemu/osdep.h"
#include "qcow2.h"
#include "trace.h"
typedef struct Qcow2CachedTable {
- int64_t offset;
- bool dirty;
- int cache_hits;
- int ref;
+ int64_t offset;
+ uint64_t lru_counter;
+ int ref;
+ bool dirty;
} Qcow2CachedTable;
struct Qcow2Cache {
- Qcow2CachedTable* entries;
- struct Qcow2Cache* depends;
+ Qcow2CachedTable *entries;
+ struct Qcow2Cache *depends;
int size;
+ int table_size;
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,
- Qcow2Cache *c, int table)
+static inline void *qcow2_cache_get_table_addr(Qcow2Cache *c, int table)
{
- BDRVQcowState *s = bs->opaque;
- return (uint8_t *) c->table_array + (size_t) table * s->cluster_size;
+ return (uint8_t *) c->table_array + (size_t) table * c->table_size;
}
-Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables)
+static inline int qcow2_cache_get_table_idx(Qcow2Cache *c, void *table)
{
- BDRVQcowState *s = bs->opaque;
+ ptrdiff_t table_offset = (uint8_t *) table - (uint8_t *) c->table_array;
+ int idx = table_offset / c->table_size;
+ assert(idx >= 0 && idx < c->size && table_offset % c->table_size == 0);
+ return idx;
+}
+
+static inline const char *qcow2_cache_get_name(BDRVQcow2State *s, Qcow2Cache *c)
+{
+ if (c == s->refcount_block_cache) {
+ return "refcount block";
+ } else if (c == s->l2_table_cache) {
+ return "L2 table";
+ } else {
+ /* Do not abort, because this is not critical */
+ return "unknown";
+ }
+}
+
+static void qcow2_cache_table_release(Qcow2Cache *c, int i, int num_tables)
+{
+/* Using MADV_DONTNEED to discard memory is a Linux-specific feature */
+#ifdef CONFIG_LINUX
+ void *t = qcow2_cache_get_table_addr(c, i);
+ int align = getpagesize();
+ size_t mem_size = (size_t) c->table_size * num_tables;
+ size_t offset = QEMU_ALIGN_UP((uintptr_t) t, align) - (uintptr_t) t;
+ size_t length = QEMU_ALIGN_DOWN(mem_size - offset, align);
+ if (mem_size > offset && length > 0) {
+ madvise((uint8_t *) t + offset, length, MADV_DONTNEED);
+ }
+#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(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(c, i - to_clean, to_clean);
+ }
+ }
+
+ c->cache_clean_lru_counter = c->lru_counter;
+}
+
+Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables,
+ unsigned table_size)
+{
+ BDRVQcow2State *s = bs->opaque;
Qcow2Cache *c;
+ assert(num_tables > 0);
+ assert(is_power_of_2(table_size));
+ assert(table_size >= (1 << MIN_CLUSTER_BITS));
+ assert(table_size <= s->cluster_size);
+
c = g_new0(Qcow2Cache, 1);
c->size = num_tables;
+ c->table_size = table_size;
c->entries = g_try_new0(Qcow2CachedTable, num_tables);
- c->table_array = qemu_try_blockalign(bs->file,
- (size_t) num_tables * s->cluster_size);
+ c->table_array = qemu_try_blockalign(bs->file->bs,
+ (size_t) num_tables * c->table_size);
if (!c->entries || !c->table_array) {
qemu_vfree(c->table_array);
return c;
}
-int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c)
+int qcow2_cache_destroy(Qcow2Cache *c)
{
int i;
static int qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i)
{
- BDRVQcowState *s = bs->opaque;
+ BDRVQcow2State *s = bs->opaque;
int ret = 0;
if (!c->entries[i].dirty || !c->entries[i].offset) {
if (c->depends) {
ret = qcow2_cache_flush_dependency(bs, c);
} else if (c->depends_on_flush) {
- ret = bdrv_flush(bs->file);
+ ret = bdrv_flush(bs->file->bs);
if (ret >= 0) {
c->depends_on_flush = false;
}
if (c == s->refcount_block_cache) {
ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_REFCOUNT_BLOCK,
- c->entries[i].offset, s->cluster_size);
+ c->entries[i].offset, c->table_size, false);
} else if (c == s->l2_table_cache) {
ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L2,
- c->entries[i].offset, s->cluster_size);
+ c->entries[i].offset, c->table_size, false);
} else {
ret = qcow2_pre_write_overlap_check(bs, 0,
- c->entries[i].offset, s->cluster_size);
+ c->entries[i].offset, c->table_size, false);
}
if (ret < 0) {
}
ret = bdrv_pwrite(bs->file, c->entries[i].offset,
- qcow2_cache_get_table_addr(bs, c, i), s->cluster_size);
+ qcow2_cache_get_table_addr(c, i), c->table_size);
if (ret < 0) {
return ret;
}
return 0;
}
-int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c)
+int qcow2_cache_write(BlockDriverState *bs, Qcow2Cache *c)
{
- BDRVQcowState *s = bs->opaque;
+ BDRVQcow2State *s = bs->opaque;
int result = 0;
int ret;
int i;
}
}
+ return result;
+}
+
+int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c)
+{
+ int result = qcow2_cache_write(bs, c);
+
if (result == 0) {
- ret = bdrv_flush(bs->file);
+ int ret = bdrv_flush(bs->file->bs);
if (ret < 0) {
result = ret;
}
for (i = 0; i < c->size; i++) {
assert(c->entries[i].ref == 0);
c->entries[i].offset = 0;
- c->entries[i].cache_hits = 0;
+ c->entries[i].lru_counter = 0;
}
- return 0;
-}
-
-static int qcow2_cache_find_entry_to_replace(Qcow2Cache *c)
-{
- int i;
- int min_count = INT_MAX;
- int min_index = -1;
+ qcow2_cache_table_release(c, 0, c->size);
+ c->lru_counter = 0;
- for (i = 0; i < c->size; i++) {
- if (c->entries[i].ref) {
- continue;
- }
-
- if (c->entries[i].cache_hits < min_count) {
- min_index = i;
- min_count = c->entries[i].cache_hits;
- }
-
- /* Give newer hits priority */
- /* TODO Check how to optimize the replacement strategy */
- if (c->entries[i].cache_hits > 1) {
- c->entries[i].cache_hits /= 2;
- }
- }
-
- if (min_index == -1) {
- /* This can't happen in current synchronous code, but leave the check
- * here as a reminder for whoever starts using AIO with the cache */
- abort();
- }
- return min_index;
+ return 0;
}
static int qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c,
uint64_t offset, void **table, bool read_from_disk)
{
- BDRVQcowState *s = bs->opaque;
+ BDRVQcow2State *s = bs->opaque;
int i;
int ret;
+ int lookup_index;
+ uint64_t min_lru_counter = UINT64_MAX;
+ int min_lru_index = -1;
+
+ assert(offset != 0);
trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache,
offset, read_from_disk);
+ if (!QEMU_IS_ALIGNED(offset, c->table_size)) {
+ qcow2_signal_corruption(bs, true, -1, -1, "Cannot get entry from %s "
+ "cache: Offset %#" PRIx64 " is unaligned",
+ qcow2_cache_get_name(s, c), offset);
+ return -EIO;
+ }
+
/* Check if the table is already cached */
- for (i = 0; i < c->size; i++) {
- if (c->entries[i].offset == offset) {
+ i = lookup_index = (offset / c->table_size * 4) % c->size;
+ do {
+ const Qcow2CachedTable *t = &c->entries[i];
+ if (t->offset == offset) {
goto found;
}
+ if (t->ref == 0 && t->lru_counter < min_lru_counter) {
+ min_lru_counter = t->lru_counter;
+ min_lru_index = i;
+ }
+ if (++i == c->size) {
+ i = 0;
+ }
+ } while (i != lookup_index);
+
+ if (min_lru_index == -1) {
+ /* This can't happen in current synchronous code, but leave the check
+ * here as a reminder for whoever starts using AIO with the cache */
+ abort();
}
- /* If not, write a table back and replace it */
- i = qcow2_cache_find_entry_to_replace(c);
+ /* Cache miss: write a table back and replace it */
+ i = min_lru_index;
trace_qcow2_cache_get_replace_entry(qemu_coroutine_self(),
c == s->l2_table_cache, i);
- if (i < 0) {
- return i;
- }
ret = qcow2_cache_entry_flush(bs, c, i);
if (ret < 0) {
BLKDBG_EVENT(bs->file, BLKDBG_L2_LOAD);
}
- ret = bdrv_pread(bs->file, offset, qcow2_cache_get_table_addr(bs, c, i),
- s->cluster_size);
+ ret = bdrv_pread(bs->file, offset,
+ qcow2_cache_get_table_addr(c, i),
+ c->table_size);
if (ret < 0) {
return ret;
}
}
- /* Give the table some hits for the start so that it won't be replaced
- * immediately. The number 32 is completely arbitrary. */
- c->entries[i].cache_hits = 32;
c->entries[i].offset = offset;
/* And return the right table */
found:
- c->entries[i].cache_hits++;
c->entries[i].ref++;
- *table = qcow2_cache_get_table_addr(bs, c, i);
+ *table = qcow2_cache_get_table_addr(c, i);
trace_qcow2_cache_get_done(qemu_coroutine_self(),
c == s->l2_table_cache, i);
return qcow2_cache_do_get(bs, c, offset, table, false);
}
-int qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table)
+void qcow2_cache_put(Qcow2Cache *c, void **table)
{
- int i;
+ int i = qcow2_cache_get_table_idx(c, *table);
- for (i = 0; i < c->size; i++) {
- if (qcow2_cache_get_table_addr(bs, c, i) == *table) {
- goto found;
- }
- }
- return -ENOENT;
-
-found:
c->entries[i].ref--;
*table = NULL;
+ if (c->entries[i].ref == 0) {
+ c->entries[i].lru_counter = ++c->lru_counter;
+ }
+
assert(c->entries[i].ref >= 0);
- return 0;
}
-void qcow2_cache_entry_mark_dirty(BlockDriverState *bs, Qcow2Cache *c,
- void *table)
+void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table)
+{
+ int i = qcow2_cache_get_table_idx(c, table);
+ assert(c->entries[i].offset != 0);
+ c->entries[i].dirty = true;
+}
+
+void *qcow2_cache_is_table_offset(Qcow2Cache *c, uint64_t offset)
{
int i;
for (i = 0; i < c->size; i++) {
- if (qcow2_cache_get_table_addr(bs, c, i) == table) {
- goto found;
+ if (c->entries[i].offset == offset) {
+ return qcow2_cache_get_table_addr(c, i);
}
}
- abort();
+ return NULL;
+}
-found:
- c->entries[i].dirty = true;
+void qcow2_cache_discard(Qcow2Cache *c, void *table)
+{
+ int i = qcow2_cache_get_table_idx(c, table);
+
+ assert(c->entries[i].ref == 0);
+
+ c->entries[i].offset = 0;
+ c->entries[i].lru_counter = 0;
+ c->entries[i].dirty = false;
+
+ qcow2_cache_table_release(c, i, 1);
}
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