Re: [PATCH] mm/uffd: UFFD_FEATURE_WP_ZEROPAGE

[Muhammad Usama Anjum]

Hi Peter,

Thank you so much for working on this.

On 2/18/23 4:10 AM, Peter Xu wrote:
> Hi, Muhammad,
> 
> On Fri, Feb 17, 2023 at 05:31:19PM +0500, Muhammad Usama Anjum wrote:
>> I've just ran my single threaded selftest [1] over an over again to get
>> some numbers.
>>
>> Without zeropage
>> qemu has 6 cores: 26.0355
> 
> Did you count in the time of read prefault?  Or did you not prefault at
> all?
No, pre-faulting is not being done in both of the runs.

Without zeropage, I'm checking pte_none() to decide if page is dirty.
With zeropage, I'm just checking if WP flag isn't set to decide if page is
dirty.

> 
>> With zeropage
>> qemu has 6 cores: 39.203
>>
>> 33% worse performance with zero pages
>>
>> Definitely, there can be better benchmark application. Please let me know
>> if I should write better benchmarks on my end.
>>
>> [1]
>> https://lore.kernel.org/all/20230202112915.867409-7-usama.anjum@xxxxxxxxxxxxx
> 
> I'll have a closer look too next week.
> 
> Thanks,
> 

-- 
BR,
Muhammad Usama Anjum