Re: [Valgrind-users] Cache conflict detection support in cachegrind

[Ivica B]

Thanks a lot :)

On Wed, Feb 8, 2023, 9:11 PM Paul Floyd  wrote:

>
>
> On 29-01-23 20:50, Ivica B wrote:
> > Hi Paul!
> >
> > I read the info you provided, but none of the programs actually
> > support detecting cache conflicts.
>
> Hi
>
> No, the tools I suggested would only give an indication, you would then
> have to use your code knowledge and maybe some trial and error to make
> improvements.
>
> Coincidentally about the same time as you asked about this I watched
> your cppcon talk an observability tools. Thumbs up.
>
> I'm looking at your bugzilla patch and will post feedback.
>
> A+
> Paul
>
>
>
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Re: [Valgrind-users] Cache conflict detection support in cachegrind

[Paul Floyd]

On 29-01-23 20:50, Ivica B wrote:

Hi Paul!

I read the info you provided, but none of the programs actually
support detecting cache conflicts.


Hi

No, the tools I suggested would only give an indication, you would then 
have to use your code knowledge and maybe some trial and error to make 
improvements.


Coincidentally about the same time as you asked about this I watched 
your cppcon talk an observability tools. Thumbs up.


I'm looking at your bugzilla patch and will post feedback.

A+
Paul



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Re: [Valgrind-users] Regarding use of Lackey to trace midway execution of a program

[Philippe Waroquiers]

If you are envisaging to modify valgrind, you could take some inspiration from 
the way
callgrind can dynamically activate/de-activate tracing.

See callgrind manual command line options and client requests for more details

Philippe


On Wed, 2023-02-08 at 17:47 +1100, Eliot Moss wrote:
> On 2/8/2023 4:10 PM, SAI GOVARDHAN M C PES1UG19EC255PESU ECE Student wrote:
> > Hi,
> > 
> > We are students working on memory access analysis, using the Lackey tool in 
> > Valgrind.
> > Our memory trace results in a large log file, and we need the trace from 
> > discrete points of 
> > execution (between 40-60%).
> > Instead of logging completely, and splitting manually, is there a way we 
> > can modify the Lackey 
> > command to pick from a desired point in the execution?
> > 
> > For reference, the command we use is
> > $ valgrind --tool=lackey --trace-mem=yes --log-file=/path_to_log ./program
> > 
> > We need to modify this to command to trace from 40-60% of the program
> 
> If you know the approximate number of memory accesses, you could do something
> as simple as:
> 
> valgrind ... | tail +n XXX | head -n YYY
> 
> to start after XXX lines of output and stop after producing YYY lines.  You
> could do something more sophisticated using, say, gawk, to trigger on a
> particular address being accessed, e.g., as an instruction fetch.
> 
> This will all slow things down a bit, but might accomplish your goals.
> 
> I'm not claiming there isn't some sophisticated way to tell valgrind when
> to start tracing, either.  Also, nobody is stopping you from customizing
> the tool yourself :-) ... a mere exercise in programming, no?
> 
> Best wishes - EM
> 
> 
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