Re: [PATCH 3/3] 64-bit futexes: x86 support

[Ulrich Drepper]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Linus Torvalds wrote:
> Also, doesn't this mean that effectively you have given up on any CPU 
> before the Pentium entirely? 

Yes, but only for the speed-up.  Not for the functionality.  All
programs will work just fine.


> Not that I want to take the patches _anyway_, but it seems doubly stupid. 
> Those things are going to be UP machines, so you could have just emulated 
> it with no correctness issues by disabling preemption.

First, you're thinking too much in kernel terms.  At userlevel I cannot
disable interrupts etc.  I cannot read 64 bits atomically on those
processors.  Second, the old implementation is not significantly slower
in normal programs on UP machines.  It's really not a big issue.


In any case, robbing 64-bit architectures of the possible performance
gain just because there are ancient versions which cannot do it is just
plain stupid.  I know you cannot suggest that.

- --
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)

iEYEARECAAYFAkhAw5QACgkQ2ijCOnn/RHTRRwCgv37woIjA5RJji4XamBQVqCyF
VMwAoIauSEdAlfK4pBJhMkIKirwEBw0z
=rDJc
-----END PGP SIGNATURE-----
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/