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Re: A Simple Real World Benchmark for cygwin

On Mon, Sep 02, 2002 at 06:02:34PM -0400, Chris Faylor wrote:
> >Here's a potential speedup for non-NTFS symlinks:
> >
> >The check_shortcut function in shortcut.c calls CoInitialize/CoUninitialize
> >for *every* .LNK it needs to check on non EA filesystems.
> >
> >I ran a small test on my computer, calling check_shortcut 1000 times.
> >When I moved the calls to CoInitialze/CoUnitialize outside the
> >check_shortcut function, the function throughput increased from 59 calls/sec
> >to 960 calls/sec.
> >
> >As it turns out, CoInit...CoUninit costs up to 20 msecs on my system.
> >
> >So my suggestion is that the CoInit../CoUnit... calls be moved to another
> >spot, to be called once per thread.
> >
> >
> >Dan.
> >
> >PS. This patch made no difference what-so-ever on the timing results of the
> >cygbench configure on my NTFS disks; then again, it may help FATxx/Samba/NFS
> >people.

Uhm... it should have nothing to do with NTFS vs. other FS.  The shortcut
symlinks are used on all FS.

> Only if there are a lot of symlinks, it seems.  Otherwise the code would never
> be hit.  And indiscriminately setting it once for each thread could have some
> negative ramifications when the program isn't manipulating any symlinks.
> It's a good suggestion, nonetheless.
> Corinna, this is your code, what do you think?  Maybe a per-thread
> "initialized_yet?" global would be useful here.

The question is if we can drop CoUninitialize() completely.  If the call
to CoUninitialize() is dropped, it should not matter to call CoInitialize()
multiple times since it should only return a "The COM library is already
initialized on this thread" return code.  That shouldn't take that much
time.  The slowness results from the need to load DLLs and such stuff.


Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                      
Red Hat, Inc.

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