Re: The cost of memory allocation

[Graham Bloice <graham.bloice () trihedral com>]

On 21 September 2016 at 10:06, Paul Offord <Paul.Offord () advance7 com> wrote:

> Good point – debug build.

Debug builds using the ms allocator are a lot slower due to all the extra
memory checking, i.e. see this page:
https://msdn.microsoft.com/en-us/library/974tc9t1.aspx

I'm not entirely certain though, that a debug build of Wireshark will use a
version of glib that then uses the debug calls into msvcrt.

However the point still stands, that using debug builds for performance
testing might not be giving you the real picture.


> *From:* wireshark-dev-bounces () wireshark org [mailto:wireshark-dev-bounces@
> wireshark.org] *On Behalf Of *Graham Bloice
> *Sent:* 21 September 2016 09:49
> *To:* Developer support list for Wireshark <wireshark-dev () wireshark org>
> *Subject:* Re: [Wireshark-dev] The cost of memory allocation
>
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> On 21 September 2016 at 09:29, Paul Offord <Paul.Offord () advance7 com>
> wrote:
>
> I’m not happy with the performance of the transum dissector and so I’ve
> started some analysis.  I’ve never used VS performance profiling before but
> I plan try to investigate this problem using it.  In the meantime I’ve used
> a tool that I’m reasonably familiar with called PerfView.  It’s produced
> some interesting results which I thought I’d share.
>
>
>
> The problem I’m having is that with transum enabled load time for a 50MB
> file increases from 5 seconds to 10 seconds, but then subsequent loads of
> the same file go out to about 40 or 50 seconds.
>
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> Above (or attached depending on your email system) is a screen shot
> showing the time spent in various functions when a load of the file took
> 44.8 seconds.  At the top of the image is a transum function called
> decode_gtcp.  The image shows that 50.7% of the total load time was spent
> executing in this function.  Then we see all of the nested functions with
> the proportion of time spent in each of those.
>
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>
> What I notice is that a lot of time is being spent in glib functions, and
> in particular the time is being spent allocating and freeing memory.
>
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> Using a slightly different view we can see that across the whole of the
> process during a load file with transum enabled more than 66% of the time
> is spent messing around with memory.
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>
> I haven’t yet figured out why I get inconsistent load times, and I don’t
> know what I can do about any of the above, but I thought it might be of
> general interest.
>
>
>
> Best regards…Paul
>
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>
> Release or debug build?
>
>
>
> --
>
> Graham Bloice
>
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-- 
Graham Bloice
Software Developer
Trihedral UK Limited

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