Re: Memory fragmentation?

On Oct 26, 7:25 pm, Mike Schroepfer <[email protected]> wrote:
> [email protected] wrote:
> > On Oct 19, 1:17 pm, Boris Zbarsky <[email protected]> wrote:
> >> Well.  In that bug the "problem" is "top reports high memory usage".
>
> > Which is typically what people complain about, too. "I closed all my
> > pages and tabs and Firefox is still using 10GB of memory!" We may have
> > free()ed almost all of it, but the library won't give it back to the
> > OS.
>
> yep - really big perceptual problem.  Just hitting spacbar in google
> reader can start to chew through ram...  Closing all tabs and having a
> very different memory number than when you first start is very hard to
> explain.  As I asked on another reply is there an easy way to get modern
> numbers on windows for this?
>
> Cheers,
>
> Schrep

I've done several tests to look in to this today.  I found an easily
reproducable testcase and ran it through purify checking memory in use
before and after (with bfcache disabled as well as images) and while
the app grows 20mb in task manager, memory in use only grows by about
1.2mb.  This leads me to believe that at least some of the numbers are
in fact due to memory fragmentation.  I did some further work to force
us to page out and back in our app which results in us landing back at
about the same amount of memory as before we loaded the page.

All that said, I have a hard time believing that we're losing 20mb to
fragmentation by loading gmail and searching and loading a message.
I'll continue to poke at this and see if I can come up with more info.

stuart