|
| From: | Alberto Garcia |
| Subject: | Re: [Qemu-devel] [PATCH 3/3] qcow2: reorder fields in Qcow2CachedTable to reduce padding |
| Date: | Tue, 26 May 2015 18:20:33 +0200 |
| User-agent: | Notmuch/0.13.2 (http://notmuchmail.org) Emacs/23.2.1 (i486-pc-linux-gnu) |
On Tue 26 May 2015 06:10:11 PM CEST, 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?
No, the size is 32 before the patch and 24 afterwards.
What you save is the 7 bytes of padding after 'dirty' and one of the
bytes after 'ref'.
>> typedef struct Qcow2CachedTable {
>> int64_t offset;
>> - bool dirty;
>> uint64_t lru_counter;
>> int ref;
>> + bool dirty;
>> } Qcow2CachedTable;
Berto
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