[lkml]   [2001]   [Apr]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: X15 alpha release: as fast as TUX but in user space (fwd)
Followup to:  <>
By author: dean gaudet <>
In newsgroup:
> On Sun, 29 Apr 2001, Jeff Garzik wrote:
> > "H. Peter Anvin" wrote:
> > > We discussed this at the Summit, not a year or two ago. x86-64 has
> > > it, and it wouldn't be too bad to do in i386... just noone did.
> >
> > It came up long before that. I refer to the technique in a post dated
> > Nov 17, even though I can't find the original.
> >
> >
> > Initiated by a post from (iirc) Dean Gaudet, we found out that
> > gettimeofday was one particular system call in the Apache fast path that
> > couldn't be optimized well, or moved out of the fast path. After a
> > couple of suggestions for improving things, Linus chimed in with the
> > magic page suggestion.
> heheh. i can't claim that i was the first ever to think of this. but
> here's the post i originally made on the topic. iirc a few folks said
> "security horror!"... then last year ingo and linus (and probably others)
> came up with a scheme everyone was happy with.
> i was kind of solving a different problem with the code page though -- the
> ability to use rdtsc on SMP boxes with processors of varying speeds and
> synchronizations.

The thing that made me say we discussed this last month was Richard's
comment that it had already been implemented (which it has, by Andrea,
for x86-64.) The idea of doing it for i386 has been kicked around for
years, originally as a way to handle INT 0x80 vs SYSENTER vs SYSCALL,
which I think is part of why it never got implemented, since handling
multiple flavours of system calls apparently causes some pain in the
system call entry/exit path.

The handling of a few things like gettimeofday etc. was something we
observed could be added on top at that time, but was largely
considered secondary.


<> at work, <> in private!
"Unix gives you enough rope to shoot yourself in the foot."
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 12:52    [W:0.079 / U:0.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site