Re: [Valgrind-developers] Bug 464103 DHAT user histogram requests

[Floyd, P. <pj...@wa...>]

Hi

On 27/01/2023 08:19, Julian Seward wrote:
> On 25/01/2023 21:16, Paul Floyd wrote:
>> I'd like some feedback on
>>
>> https://bugs.kde.org/show_bug.cgi?id=464103
>>
>> This allows the user to specify that a block of memory should be 
>> histogrammed. [..]
>
> I can see that the request tells dhat to start tracking the area. How 
> does it
> know when to stop tracking?  And what happens if the area happens to 
> overlap
> an existing area?

I didn't have any plans for stopping - just leave that to DHAT to stop 
when the memory is feeed/reallocd.

>
> Rather than specify exactly the bounds of the area in the macro (that 
> is, both
> address and length), would it be preferable to just specify the base 
> address
> of the block, in the expectation that the block is one that the 
> program has
> previously obtained from malloc, and hence one that dhat already knows 
> about?
>
Good idea. I was just copying the code that creates the blocks and 
propagating the arguments back out to the client requests.

> In this case, the macro is merely a request to say "please histogram 
> this block even though it's above the 1024 limit".  That seems to me 
> at least to
> be a simple mental model for end users.  For the [start, +len) 
> formulation in
> the existing patch, I'm unclear how that interacts with the "normal" 
> machinery
> of tracking only blocks that come from malloc.

My intention is this this to be an override for the 1024 limit.


I'll remove the size argument.

A+

Paul