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Re: PATCH: Turn on -fomit-frame-pointer by default for 32bit Linux/x86
On Wed, Aug 4, 2010 at 10:47 AM, Andrew Haley <aph@redhat.com> wrote:
> On 08/04/2010 06:41 PM, H.J. Lu wrote:
>> On Wed, Aug 4, 2010 at 10:35 AM, Andi Kleen <andi@firstfloor.org> wrote:
>>> "H.J. Lu" <hjl.tools@gmail.com> writes:
>>>>
>>>> Can we find if oprofile works with -fomit-frame-pointer on 32bit Linux/x86.
>>>
>>> It doesn't for user space. The problem is that you would need
>>> an in kernel dwarf2 unwinder that reads user space tables.
>>>
>>> x86-64 suffers from this already.
>>
>
>> But it is considered acceptable
>
> By whom?
By people's action.
>
>> so that we still want -fomit-frame-pointer for Linux/x86-64.
>
> Ah, so your argument *is* "x86-64 profiling is degraded, so we might
> as well degrade x86 as well."
>
Yes, especially when it gives some nice performance improvement.
Can you tell me which gcc optimization can give you 4% speedup
in most applications?
--
H.J.