Re: [Chromium-dev] It's the calls to FD_ZERO sucking performance

[Alan M. <al...@re...>]

On Thu, 2004-06-17 at 08:57, Martins D Innus wrote:
> Mike,
> 	I found the same thing when I was profiling tilesort last week.
> Seems to be doing Recv due to Sync on Swap. I guess the FD_ZERO just takes
> the most time in that loop.  The problem I found with oprofile was that I
> could not get it to tell me how many times a function was called, only how
> much time was spent in a function.  I was able to get gmon.out and bb.out
> on the crserver side by compiling with "-pg -a" but never got a gmon.out
> with any chromium calls in it on the app side (only function calls from my
> application), even when doing the symlink trick and not using crappfaker.
> bb.out has some decent information in it but some of the files I get are
> corrupted so I don't know how much they can be trusted.
> 
If you are running with a 2.6 kernel with oprofile enabled you can run
opstack to get gprof like output.
see http://oprofile.sourceforge.net/doc/opstack.html

You have to apply a kernel patch to make it work though.The web page I'm
referring to has a link to it.


> Oh, also the "make profile" target is slightly broken( at least in the cr
> version I was using).  In cr.mk PROFILE_LAGS should be PROFILE_FLAGS and
> in Linux.mk PROFILEFLAGS should be PROFILE_FLAGS.
> 
> Let me know if you come up with any profiling tricks.
> 
> Martins
> 
> On Wed, 16 Jun 2004, Mike Houston wrote:
> 
> > It's packspu_context that calls crNetRecv()...  Apparently, we call 
> > packspu_CreateContext repeatedly and do:
> > 
> > while(writeback)
> >    crNetRecv();
> > 
> > Here is where time is getting sucked away.  I fear that we probably do 
> > something similar in the tilesort spu...
> > 
> > -Mike
> > 
> > Mike Houston wrote:
> > 
> > > According to the code annotations, thanks again Alan!, the calls to 
> > > FD_ZERO in the recv functions for both SDP and TCP are quite 
> > > expensive.  What's odd is that it's the appfaker side that is getting 
> > > creamed by the FD_ZERO in recv.  What the heck is the appfaker doing 
> > > recv's for?!
> > >
> > > -Mike
> > >
> > >
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> -----------------------------------------------------------------------
> Martins Innus				(716) 645-6500 x534
> Scientific Visualization Specialist	mi...@cc...
> Center for Computational Research	www.ccr.buffalo.edu/martins.htm
> University at Buffalo
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