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From: | Max Reitz |
Subject: | Re: [Qemu-devel] [PATCH 3/3] qcow2: reorder fields in Qcow2CachedTable to reduce padding |
Date: | Tue, 26 May 2015 18:14:09 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 26.05.2015 18:12, Eric Blake wrote:
On 05/26/2015 10:10 AM, Max Reitz wrote:On 18.05.2015 18:48, Alberto Garcia wrote:Changing the current ordering saves 8 bytes per cache entry in x86_64.Hm, not seven?Signed-off-by: Alberto Garcia <address@hidden> --- block/qcow2-cache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c index a215f5b..43590ff 100644 --- a/block/qcow2-cache.c +++ b/block/qcow2-cache.c @@ -31,9 +31,9 @@ typedef struct Qcow2CachedTable { int64_t offset; - bool dirty; uint64_t lru_counter; int ref; + bool dirty; } Qcow2CachedTable; struct Qcow2Cache {With "7" above, or an explanation why it actually is 8:Old layout: 0-7 offset 8 dirty 9-15 padding 16-23 lru_counter 24-27 dirty 28-31 padding New layout: 0-7 offset 8-15 lru_counter 16-19 ref 20 dirty 21-23 padding It indeed saves 8 bytes.
Oh, I forgot about the padding at the end. Thanks! Max
Reviewed-by: Max Reitz <address@hidden>
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