(no subject)

[Anoop J.]

How is this different from a fully associative cache .Would be better if u
could deal it based on the address bits used

Thanks

David Lang wrote:

>The idea of page coloring is based on the fact that common implementations
>of caching can't put any page in memory in any line in the cache (such an
>implementation is possible, but is more expensive to do so is not commonly
>done)
>
>With this implementation it means that if your program happens to use
>memory that cannot be mapped to half of the cache lines then effectivly
>the CPU cache is half it's rated size for your program. the next time your
>program runs it may get a more favorable memory allocation and be able to
>use all of the cache and therefor run faster.
>
>Page coloring is an attampt to take this into account when allocating
>memory to programs so that every program gets to use all of the cache.
>
>David Lang
>
>
> On Fri, 24 Jan 2003, Anoop J. wrote:
>
>>Date: Fri, 24 Jan 2003 10:38:03 +0530 (IST)
>>From: Anoop J. <cs99001@nitc.ac.in>
>>To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
>>
>>
>>How does page coloring work. Iwant its mechanism not the implementation.
>>I went through some pages of W.L.Lynch's paper on cache and VM. Still not
>>able to grasp it .
>>
>>
>>Thanks in advance
>>
>>
>>
>>-
>>To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>the body of a message to majordomo@vger.kernel.org
>>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>Please read the FAQ at  http://www.tux.org/lkml/
>>
>

Re: your mail

[David Lang]

implementing a fully associative cache eliminates the need for page
coloring, but it has to be implemented in hardware. if you don't have
fully associative caches in your hardware page coloring helps avoid the
worst case memory allocations.

from what I have seen on the attempts to implement it the problem is that
the calculations needed to do page colored allocations end up costing
enough that they end up with a net loss compared to the old method.

David Lang


 On Fri, 24 Jan 2003, Anoop J.
wrote:

> Date: Fri, 24 Jan 2003 11:24:24 +0530 (IST)
> From: Anoop J. <cs99001@nitc.ac.in>
> To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
>
>
> How is this different from a fully associative cache .Would be better if u
> could deal it based on the address bits used
>
> Thanks
>
> David Lang wrote:
>
> >The idea of page coloring is based on the fact that common implementations
> >of caching can't put any page in memory in any line in the cache (such an
> >implementation is possible, but is more expensive to do so is not commonly
> >done)
> >
> >With this implementation it means that if your program happens to use
> >memory that cannot be mapped to half of the cache lines then effectivly
> >the CPU cache is half it's rated size for your program. the next time your
> >program runs it may get a more favorable memory allocation and be able to
> >use all of the cache and therefor run faster.
> >
> >Page coloring is an attampt to take this into account when allocating
> >memory to programs so that every program gets to use all of the cache.
> >
> >David Lang
> >
> >
> > On Fri, 24 Jan 2003, Anoop J. wrote:
> >
> >>Date: Fri, 24 Jan 2003 10:38:03 +0530 (IST)
> >>From: Anoop J. <cs99001@nitc.ac.in>
> >>To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
> >>
> >>
> >>How does page coloring work. Iwant its mechanism not the implementation.
> >>I went through some pages of W.L.Lynch's paper on cache and VM. Still not
> >>able to grasp it .
> >>
> >>
> >>Thanks in advance
> >>
> >>
> >>
> >>-
> >>To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> >>the body of a message to majordomo@vger.kernel.org
> >>More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>Please read the FAQ at  http://www.tux.org/lkml/
> >>
> >
>
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>

Re: your mail

[David Lang]

I think this is a case of the same tuerm being used for two different
purposes. I don't know the use you are refering to.

David Lang


On Fri, 24 Jan 2003, Anoop J. wrote:

> I read that the data coherency problem due to virtual indexing is avoided
> through page coloring and it has also got the speed of physical indexing
> can u just elaborate on how this is possible?
>
>
> Thanks
>
>
>
>
> > implementing a fully associative cache eliminates the need for page
> > coloring, but it has to be implemented in hardware. if you don't have
> > fully associative caches in your hardware page coloring helps avoid the
> > worst case memory allocations.
> >
> > from what I have seen on the attempts to implement it the problem is
> > that the calculations needed to do page colored allocations end up
> > costing enough that they end up with a net loss compared to the old
> > method.
> >
> > David Lang
> >
> >
> >  On Fri, 24 Jan 2003, Anoop J.
> > wrote:
> >
> >> Date: Fri, 24 Jan 2003 11:24:24 +0530 (IST)
> >> From: Anoop J. <cs99001@nitc.ac.in>
> >> To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
> >>
> >>
> >> How is this different from a fully associative cache .Would be better
> >> if u could deal it based on the address bits used
> >>
>
>
>

Re: your mail

[Anoop J.]

I read that the data coherency problem due to virtual indexing is avoided
through page coloring and it has also got the speed of physical indexing
can u just elaborate on how this is possible?


Thanks




> implementing a fully associative cache eliminates the need for page
> coloring, but it has to be implemented in hardware. if you don't have
> fully associative caches in your hardware page coloring helps avoid the
> worst case memory allocations.
>
> from what I have seen on the attempts to implement it the problem is
> that the calculations needed to do page colored allocations end up
> costing enough that they end up with a net loss compared to the old
> method.
>
> David Lang
>
>
>  On Fri, 24 Jan 2003, Anoop J.
> wrote:
>
>> Date: Fri, 24 Jan 2003 11:24:24 +0530 (IST)
>> From: Anoop J. <cs99001@nitc.ac.in>
>> To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
>>
>>
>> How is this different from a fully associative cache .Would be better
>> if u could deal it based on the address bits used
>>

Re: your mail

[Anoop J.]

ok i shall put it in another way
since virtual indexing is a representation of the virtual memory,
it is possible for more multiple virtual addresses to represent the same
physical address.So the problem of aliasing occurs in the cache.Does page
coloring guarantee a unique mapping of physical address.If so how is the
maping from virtual to physical address



Thanks



> I think this is a case of the same tuerm being used for two different
> purposes. I don't know the use you are refering to.
>
> David Lang
>
>
>

Re: your mail

[David Lang]

the cache never sees the virtual addresses, it operated excclusivly on the
physical addresses so the problem of aliasing never comes up.

virtual to physical addres mapping is all resolved before anything hits
the cache.

David Lang

On Fri, 24 Jan 2003, Anoop J. wrote:

> Date: Fri, 24 Jan 2003 15:19:16 +0530 (IST)
> From: Anoop J. <cs99001@nitc.ac.in>
> To: david.lang@digitalinsight.com
> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org
> Subject: Re: your mail
>
> ok i shall put it in another way
> since virtual indexing is a representation of the virtual memory,
> it is possible for more multiple virtual addresses to represent the same
> physical address.So the problem of aliasing occurs in the cache.Does page
> coloring guarantee a unique mapping of physical address.If so how is the
> maping from virtual to physical address
>
>
>
> Thanks
>
>
>
> > I think this is a case of the same tuerm being used for two different
> > purposes. I don't know the use you are refering to.
> >
> > David Lang
> >
> >
> >
>
>
>
>

Re: your mail

[Maciej W. Rozycki]

On Fri, 24 Jan 2003, David Lang wrote:

> the cache never sees the virtual addresses, it operated excclusivly on the
> physical addresses so the problem of aliasing never comes up.

 It depends on the implementation.

> virtual to physical addres mapping is all resolved before anything hits
> the cache.

 It depends on the processor.

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +