Cygwin Filesystem Performance degradation 1.7.5 vs 1.7.7, and methods for improving performance

Corinna Vinschen
Wed Sep 29 08:32:00 GMT 2010

On Sep 29 05:50, Andy Koppe wrote:
> On 28 September 2010 18:44, Warren Young wrote:
> > On 9/28/2010 9:10 AM, Christopher Faylor wrote:
> >>
> >> It isn't extremely surprising that Linux access speed for a filesystem
> >> in a simulated environment, which presumably does not go through
> >> multiple layers of DLLs, would be faster than Cygwin.
> >
> > I think it more likely that the HGFS driver doesn't try to preserve full
> > POSIX semantics.  There's plenty of precedent: vfat, iso9660...  One could
> > probably verify this faster by examining the driver's source code
> > ( than by tracing syscalls.
> >
> > If that's the explanation, it points at a possible path forward.
> >
> > On Linux, these secondary filesystems aren't expected to provide full POSIX
> > semantics, simply because they are secondary.  No one cries very hard that
> > you can't make symlinks on a FAT-formatted USB stick.
> >
> > Yet, there's probably no technical reason you couldn't get a POSIX-like
> > system to run on a crippled filesystem.  It's probably even been done lots
> > of times before in the embedded world.  Some of the PC Unix systems from the
> > 80s and early 90s were pretty screwy in this way, too.  Screwy doesn't
> > prevent you from doing useful work, though.
> >
> > Would it not be useful to have a mode in Cygwin that purposely skips any
> > POSIX semantics that it can't get for free by making the POSIX syscalls
> > nothing more than thin wrappers around the nearest equivalent Win32 API?  If
> > you put it in this mode and it breaks, you get to keep both pieces.  There
> > are those who would happily accept the speed increase for loss of some
> > functionality.  I wouldn't, but some would.  I'd bet a lot of the 3PPs are
> > in that group, since they know their target environment very well.
> Doesn't the 'noacl' mount option provide that already?

Partially, there are also the ihash and the exec/notexec options.  A lot
has been already discussed on the cygwin-patches list, see, for instance



Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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