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DateFri, 04 Apr 2008 00:58:00 +0530
FromBalbir Singh <>
SubjectRe: [-mm] Add an owner to the mm_struct (v7)
Paul Menage wrote:
> On Thu, Apr 3, 2008 at 11:51 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>> >> + * delay_group_leader() ensures that if the group leader is around
>> >> + * we need not select a new owner.
>> >> + */
>> >> + ret = (mm && (atomic_read(&mm->mm_users) > 1) && (mm->owner == p) &&
>> >> + !delay_group_leader(p));
>> >> + return ret;
>> >> +}
>> >
>> > Ugh. Could you please spell this out a bit more. I find that stuff
>> > above really hard to read. Something like:
>> >
>> > if (!mm)
>> > return 0;
>> > if (atomic_read(&mm->mm_users) <= 1)
>> > return 0;
>> > if (mm->owner != p)
>> > return 0;
>> > if (delay_group_leader(p))
>> > return 0;
>> > return 1;
>> >
>>
>> The problem with code above is 4 branch instructions and the code I have just 4
>> AND operations.
>
> They'll be completely equivalent to the compiler, due to the
> short-circuit evaluation of &&

Aahh.. Yes.. my bad.. I keep under-estimating compilers and their potential to
optimize

Form (2) seems more readable, I'll move to that



--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL


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