Re: [PATCH] Save some bytes in mm_struct by filling holes on 64bit

Lennart Sorensen
2008-03-13T16:40:42Z

On Wed, Mar 12, 2008 at 03:28:07PM +0100, Andi Kleen wrote:
>
> Save some bytes in mm_struct by filling holes
>
> Putting int values together for better packing on 64bit
> shrinks sizeof(struct mm_struct) from 776 bytes to 760 bytes.

Are you going to fix the nice comments that mentioned what feature they
were part of now that things are all mixed together? I wonder if a few
bytes aren't worth paying for readable code.

After all now some 'aio bits' things are not in the 'aio bits' labeled
section.

> Signed-off-by: Andi Kleen <ak@suse.de>
>
> Index: linux-2.6.25-rc5/include/linux/mm_types.h
> ===================================================================
> --- linux-2.6.25-rc5.orig/include/linux/mm_types.h
> +++ linux-2.6.25-rc5/include/linux/mm_types.h
> @@ -172,6 +172,7 @@ struct mm_struct {
> atomic_t mm_users; /* How many users with user space? */
> atomic_t mm_count; /* How many references to "struct mm_struct" (users count as 1) */
> int map_count; /* number of VMAs */
> + rwlock_t ioctx_list_lock; /* aio lock */
> struct rw_semaphore mmap_sem;
> spinlock_t page_table_lock; /* Protects page tables and some counters */
>
> @@ -213,14 +214,13 @@ struct mm_struct {
> unsigned int token_priority;
> unsigned int last_interval;
>
> + int core_waiters;
> unsigned long flags; /* Must use atomic bitops to access the bits */
>
> /* coredumping support */
> - int core_waiters;
> struct completion *core_startup_done, core_done;
>
> /* aio bits */
> - rwlock_t ioctx_list_lock;
> struct kioctx *ioctx_list;
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> struct mem_cgroup *mem_cgroup;
> --

--
Len Sorensen