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Re: [Qemu-block] [PATCH v6 5/8] qcow2: Increase the default upper limit

From: Eric Blake
Subject: Re: [Qemu-block] [PATCH v6 5/8] qcow2: Increase the default upper limit on the L2 cache size
Date: Thu, 9 Aug 2018 17:03:53 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0

On 08/09/2018 04:53 PM, Leonid Bloch wrote:
The upper limit on the L2 cache size is increased from 1 MB to 32 MB.
This is done in order to allow default full coverage of an image with
the L2 cache for images of up to 256 GB in size (was 8 GB). Note, that
only the needed amount to cover the full image is allocated. The value
which is changed here is just the upper limit on the L2 cache size,
beyond which it will not grow, even if the size of the image requires
it to.

Signed-off-by: Leonid Bloch <address@hidden>
  block/qcow2.h        | 2 +-
  docs/qcow2-cache.txt | 6 +++---
  qemu-options.hx      | 2 +-
  3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 0bab3d8b94..d77a31d932 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -73,7 +73,7 @@
  /* Must be at least 4 to cover all cases of refcount table growth */
  #define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */
-#define DEFAULT_L2_CACHE_MAX_SIZE 1048576 /* bytes */
+#define DEFAULT_L2_CACHE_MAX_SIZE 0x2000000U /* bytes */

I'd spell this as '(64 * MiB)' with the help of "qemu/units.h".

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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