On Tue, Mar 10, 2009 at 03:37:18PM +0100, Nick Piggin wrote:
> costly, unfortunately). It results in about 900 bytes smaller code too. It
> does increase the size of a vfsmount, however.
Only on 64-bit SMP systems, and then only by four bytes. And, best of
all, you can fix that if you care. Look at this:
/* --- cacheline 1 boundary (64 bytes) --- */
struct list_head mnt_child; /* 64 16 */
int mnt_flags; /* 80 4 */
/* XXX 4 bytes hole, try to pack */
const char * mnt_devname; /* 88 8 */
struct list_head mnt_list; /* 96 16 */
struct list_head mnt_expire; /* 112 16 */
So move mnt_flags to later in the struct (after the pointers), and move
> +#ifdef CONFIG_SMP
> + int *mnt_writers;
> +#else
> + int mnt_writers;
> +#endif
to be with the other pointers. Bonus points for putting it between
struct mnt_namespace * mnt_ns; /* 184 8 */
and
int mnt_id; /* 192 4 */
so that it doesn't become a new 4-byte hole for those incredibly common
64-bit uniprocessor builds. *cough*.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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