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[Qemu-devel] [PULL 12/16] qcow2: mark the memory as no longer needed aft
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 12/16] qcow2: mark the memory as no longer needed after qcow2_cache_empty() |
Date: |
Fri, 4 Sep 2015 22:10:43 +0200 |
From: Alberto Garcia <address@hidden>
After having emptied the cache, the data in the cache tables is no
longer useful, so we can tell the kernel that we are done with it. In
Linux this frees the resources associated with it.
The effect of this can be seen in the HMP commit operation: it moves
data from the top to the base image (and fills both caches), then it
empties the top image. At this point the data in that cache is no
longer needed so it's just wasting memory.
Signed-off-by: Alberto Garcia <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Message-id: address@hidden
Signed-off-by: Max Reitz <address@hidden>
---
block/qcow2-cache.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c
index 53b8afc..f63e7d8 100644
--- a/block/qcow2-cache.c
+++ b/block/qcow2-cache.c
@@ -22,8 +22,16 @@
* THE SOFTWARE.
*/
+/* Needed for CONFIG_MADVISE */
+#include "config-host.h"
+
+#if defined(CONFIG_MADVISE) || defined(CONFIG_POSIX_MADVISE)
+#include <sys/mman.h>
+#endif
+
#include "block/block_int.h"
#include "qemu-common.h"
+#include "qemu/osdep.h"
#include "qcow2.h"
#include "trace.h"
@@ -60,6 +68,22 @@ static inline int qcow2_cache_get_table_idx(BlockDriverState
*bs,
return idx;
}
+static void qcow2_cache_table_release(BlockDriverState *bs, Qcow2Cache *c,
+ int i, int num_tables)
+{
+#if QEMU_MADV_DONTNEED != QEMU_MADV_INVALID
+ BDRVQcowState *s = bs->opaque;
+ void *t = qcow2_cache_get_table_addr(bs, c, i);
+ int align = getpagesize();
+ size_t mem_size = (size_t) s->cluster_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 (length > 0) {
+ qemu_madvise((uint8_t *) t + offset, length, QEMU_MADV_DONTNEED);
+ }
+#endif
+}
+
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables)
{
BDRVQcowState *s = bs->opaque;
@@ -237,6 +261,8 @@ int qcow2_cache_empty(BlockDriverState *bs, Qcow2Cache *c)
c->entries[i].lru_counter = 0;
}
+ qcow2_cache_table_release(bs, c, 0, c->size);
+
c->lru_counter = 0;
return 0;
--
1.8.3.1
- [Qemu-devel] [PULL 02/16] qemu-iotests: disable default qemu devices for cross-platform compatibility, (continued)
- [Qemu-devel] [PULL 02/16] qemu-iotests: disable default qemu devices for cross-platform compatibility, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 05/16] qemu-iotests: s390x: fix test 130, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 07/16] qemu-img: Fix crash in amend invocation, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 06/16] block/raw-posix: Use raw_normalize_devicepath(), Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 08/16] iotests: More options for VM.add_drive(), Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 09/16] iotests: Respect -nodefaults in tests 41 and 55, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 10/16] iotests: Do not suppress segfaults in bash tests, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 11/16] iotests: Warn if python subprocess is killed, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 15/16] qcow2: reorder fields in Qcow2CachedTable to reduce padding, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 14/16] docs: document how to configure the qcow2 L2/refcount caches, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 12/16] qcow2: mark the memory as no longer needed after qcow2_cache_empty(),
Kevin Wolf <=
- [Qemu-devel] [PULL 16/16] quorum: validate vote threshold against num_children even if read-pattern is fifo, Kevin Wolf, 2015/09/04
- [Qemu-devel] [PULL 13/16] qcow2: add option to clean unused cache entries after some time, Kevin Wolf, 2015/09/04
- Re: [Qemu-devel] [PULL 00/16] Block patches, Peter Maydell, 2015/09/07