[PATCH 1/7] cgroups: Shrink struct cgroup_subsys

Paul Menage menage at google.com
Tue Nov 9 17:53:13 PST 2010

On Tue, Nov 9, 2010 at 4:52 PM, Li Zefan <lizf at cn.fujitsu.com> wrote:
>> bool active:1;
>> bool disabled:1;
> It won't compile, but unsigned char active:1 will do. ;)

Are you sure? I don't have a buildable kernel tree at the moment, but
the following fragment compiled fine for me (with gcc 4.4.3):

struct foo {
  _Bool b1:1;
  _Bool b2:1;

and was sized at one byte. And "bool" is just a typedef of _Bool in
the kernel headers.

> Every thing that reduces code size (without sacrifice readability
> and maintain maintainability) should be worth.

Agreed, within reason. But this patch doesn't reduce code size - it
makes the code fractionally more complicated and reduces the *binary*
size by a few bytes.

> This is one of the reasons we accept patches that replacing
> kmalloc+memset with kzalloc, which just saves 8 bytes in my box.

Replacing two function calls with one function call is a code
simplification and hence (generally) a good thing - the minuscule
reduction in binary size reduction that comes with it is just noise.


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