[Qemu-devel] [PATCH v3 4/5] qcow2: Set the default cache-clean-interval to 30 seconds

[Leonid Bloch <lbloch@janustech.com>]

The default cache-clean-interval is set to 30 seconds, in order to lower
the overhead of the qcow2 caches (before the default was 0, i.e.
disabled).

Signed-off-by: Leonid Bloch <lbloch@janustech.com>
---
 block/qcow2.c        | 2 +-
 block/qcow2.h        | 1 +
 docs/qcow2-cache.txt | 4 ++--
 qapi/block-core.json | 3 ++-
 qemu-options.hx      | 2 +-
 5 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index f60cb92169..453a6377ac 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -941,7 +941,7 @@ static int qcow2_update_options_prepare(BlockDriverState *bs,
     /* New interval for cache cleanup timer */
     r->cache_clean_interval =
         qemu_opt_get_number(opts, QCOW2_OPT_CACHE_CLEAN_INTERVAL,
-                            s->cache_clean_interval);
+                            DEFAULT_CACHE_CLEAN_INTERVAL);
 #ifndef CONFIG_LINUX
     if (r->cache_clean_interval != 0) {
         error_setg(errp, QCOW2_OPT_CACHE_CLEAN_INTERVAL
diff --git a/block/qcow2.h b/block/qcow2.h
index d77a31d932..96a2808685 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -77,6 +77,7 @@
 
 #define DEFAULT_CLUSTER_SIZE 65536
 
+#define DEFAULT_CACHE_CLEAN_INTERVAL 30  /* seconds */
 
 #define QCOW2_OPT_LAZY_REFCOUNTS "lazy-refcounts"
 #define QCOW2_OPT_DISCARD_REQUEST "pass-discard-request"
diff --git a/docs/qcow2-cache.txt b/docs/qcow2-cache.txt
index c7625cdeb3..c795febbdc 100644
--- a/docs/qcow2-cache.txt
+++ b/docs/qcow2-cache.txt
@@ -202,8 +202,8 @@ This example removes all unused cache entries every 15 minutes:
 
    -drive file=hd.qcow2,cache-clean-interval=900
 
-If unset, the default value for this parameter is 0 and it disables
-this feature.
+If unset, the default value for this parameter is 30. Setting it to 0
+disables this feature.
 
 Note that this functionality currently relies on the MADV_DONTNEED
 argument for madvise() to actually free the memory. This is a
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 5b9084a394..f98cd14740 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2830,7 +2830,8 @@
 #
 # @cache-clean-interval:  clean unused entries in the L2 and refcount
 #                         caches. The interval is in seconds. The default value
-#                         is 0 and it disables this feature (since 2.5)
+#                         is 30. Setting 0 disables this feature. (since 2.5)
+#
 # @encrypt:               Image decryption options. Mandatory for
 #                         encrypted images, except when doing a metadata-only
 #                         probe of the image. (since 2.10)
diff --git a/qemu-options.hx b/qemu-options.hx
index d6e15b2f06..a0e0763f71 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -767,7 +767,7 @@ it which is not used for the L2 cache)
 
 @item cache-clean-interval
 Clean unused entries in the L2 and refcount caches. The interval is in seconds.
-The default value is 0 and it disables this feature.
+The default value is 30. Setting it to 0 disables this feature.
 
 @item pass-discard-request
 Whether discard requests to the qcow2 device should be forwarded to the data
-- 
2.17.1