Messages in this thread | | | Date | Sun, 9 Jul 2006 19:34:04 -0400 | From | Chuck Ebbert <> | Subject | Re: [patch] i386: use thread_info flags for debug regs and IO bitmaps |
| |
In-Reply-To: <Pine.LNX.4.64.0607081425430.3869@g5.osdl.org>
On Sat, 8 Jul 2006 14:26:53 -0700, Linus Torvalds wrote: > > On Fri, 7 Jul 2006, Chuck Ebbert wrote: > > > > From: Stephane Eranian <eranian@hpl.hp.com> > > > > Use thread info flags to track use of debug registers and IO bitmaps. > > > > - add TIF_DEBUG to track when debug registers are active > > - add TIF_IO_BITMAP to track when I/O bitmap is used > > - modify __switch_to() to use the new TIF flags > > Can you explain what the advantages of this are?
Stephane's perfmon2 patch adds yet another special-case to the switch_to() code, so Andi suggested this change. It will allow the perfmon2 patch to have no performance impact on normal task-switching, since it will just use another flag.
After I saw a ~7% gain in task-switch performance, I like it now even without perfmon2 in there.
> I don't see it. It's just creating new state to describe state that we > already had, and as far as I can tell, it's just a way to potentially have > more new bugs thanks to the new state getting out of sync with the old > one?
Well yeah, there is that. But Andi and I both reviewed it and he's already put the x86_64 version into his tree. Testing in -mm should show whether there are any problems.
-- Chuck "You can't read a newspaper if you can't read." --George W. Bush - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |