Re: The cost of memory allocation

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

On 21 September 2016 at 10:12, Graham Bloice <graham.bloice () trihedral com>
wrote:

> 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.

And this post explains how even a release build is affected by debug memory
allocations if it's run under a debugger:
http://preshing.com/20110717/the-windows-heap-is-slow-when-launched-from-the-debugger/


> > *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
> >
> >
> >
> >
> >
> >
> >
> > 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.
> >
> >
> >
> >
> >
> > 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.
> >
> >
> >
> > 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.
> >
> >
> >
> >
> >
> > 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.
> >
> >
> >
> > 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
> >
> >
> >
> >
> >
> > Release or debug build?
> >
> >
> >
> > --
> >
> > Graham Bloice
> --
> Graham Bloice

-- 
Graham Bloice

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