Andrew,
I compile the release version of the test code with VC 6.0 and run it on windows xp sp2 , but it took the same time in every try_throw_catch block ,so perhaps we can do something to improve the preformance
Miles
> 发件人: Andrew Haley <aph@xxxxxxxxxx>
> 主题: Re: Anybody may help to explain the issue of the source code , next "try-throw-catch" will cost more cpu time than previous one
> 收件人: "f z" <zhangjiakouzf@xxxxxxxxxxxx>
> 抄送: gcc-help@xxxxxxxxxxx
> 日期: 2009,12,周五,12:56上午
> f z wrote:
> > Happy New Year! Haley,
>
> And a Happy New Year to you.
>
> > Thanks for your help!
> >
> > In your result , there isn't any variation in the
> time taken.
> >
> > My test code can be like this :
> >
> > while(1){
> > try_throw_catch_block(0); // it takes about 133xxxxx
> every time
> > try_throw_catch_block(1); // it takes about 148xxxxx
> every time
> > try_throw_catch_block(2); // it takes about 158xxxxx
> every time
> > try_throw_catch_block(3); // it takes about 172xxxxx
> every time
> > }
>
> > In my opinion , next "try_throw_catch" in
> writing order will takes more cpu time than the previous
> one.
> >
> > Then , I will use oprofile to check it.
>
> Yes, I see the same result as you.
>
> I think I might know what is happening. When a throw is
> caught, there
> is a search for the catch region.
>
> _Unwind_IteratePhdrCallback searches for the eh_frame that
> contains
> the PC we're looking for. There is a binary search for
> the catch
> region. Like all binary searches, this is not constant
> time, so I
> suspect that's what we're seeing.
>
> Andrew.
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