[Development] Question about QCoreApplicationData::*_libpaths

[Hausmann Simon]

Hi,

Could you elaborate where you see copy on write causing writes to shared cache lines? Are you concerned about the shared cache line for the reference count?

For reading MESI allows for shared cache lines and for hyper threads the shared l1 data cache mode favors sharing and thus CoW.

What am I missing to understand your statement?


Simon

  Original Message
From: Bubke Marco
Sent: Sunday, January 24, 2016 19:10
To: Kevin Kofler; development at qt-project.org
Subject: Re: [Development] Question about QCoreApplicationData::*_libpaths


On January 24, 2016 17:45:36 Kevin Kofler <kevin.kofler at chello.at> wrote:

> Marc Mutz wrote:
>> (numThread == 2, same box)
>>
>> Copying is still not significantly slower than ref-counting, even for 4K
>> elements.
>
> But it is already slower with as little as 32 elements, and stops being
> significantly faster already at 16 elements.
>
> And now try with numThread == 1 for some extra fun. :-) A lot of code out
> there is still single-threaded.
>

 Yes but in the future the processors getting more and more parallel. If I am working on the bigger dataset with parallel algorithms I don't want to share writes to the same cache like. Something which CoW is providing.

>         Kevin Kofler
>
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> Development at qt-project.org
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--
Sent from cellphone, sorry for the typos
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