[PATCH 1/2] arm64:vdso: Rewrite gettimeofday into C.
apinski at caviumnetworks.com
Mon Apr 24 14:49:10 EDT 2017
On 4/24/2017 8:21 AM, Catalin Marinas wrote:
> On Sun, Apr 23, 2017 at 04:47:00PM -0700, Andrew Pinski wrote:
>> This allows the compiler to optimize the divide by 1000.
>> And remove the other divide.
>> On ThunderX, gettimeofday improves by 32%. On ThunderX 2,
>> gettimeofday improves by 18%.
> Is this with or without the second patch (removing the ISB)?
This is without the second patch that removes the ISB. Maybe I
should not have sent them as the same patch set to make it clear that
way. As I tried to make a mention of, the improvement is the compiler
not outputting the udiv instruction for the division by 1000. I
should also mention I tested this patch on a softiron using GCC 4.8.5
(SUSE's default compiler) and the performance was the same; GCC 4.8.5
emits udiv still in this case. I did not try a newer compiler to see
the performance there.
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