From: Gabriel Paubert <paubert@iram.es>
To: malc <av1474@comtv.ru>
Cc: linuxppc-dev@lists.ozlabs.org, hollis@penguinppc.org
Subject: Re: Probing for native availability of isel from userspace
Date: Sat, 22 Sep 2012 12:21:51 +0200 [thread overview]
Message-ID: <20120922102151.GA31314@visitor2.iram.es> (raw)
In-Reply-To: <alpine.LNX.2.00.1209221412010.1468@linmac>
On Sat, Sep 22, 2012 at 02:12:42PM +0400, malc wrote:
> On Sat, 22 Sep 2012, Segher Boessenkool wrote:
>
> > > Is it possible to determine if _native_ isel is available from userspace
> > > somehow?
> >
> > Just try to execute one and catch the SIGILL?
> >
>
> Unfortunately my kernel emulates ISEL for me in this case, so i don't
> get any SIGILLs.
Perform a few isels in a loop between a couple of mftb and measure the
shortest time it takes. Any emulation will take tens of timebase ticks,
hardware implementation will return very small values, perhaps even
0 depending on the relationship between core and timebase frequencies.
I don't remember whether it's necessary inserting an isync between the
two mftb. I believe that even on the most OOO machines, two mftb in
a row will not be reordered to the point that the second executes before
the first.
Gabriel
next prev parent reply other threads:[~2012-09-22 11:28 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-21 20:05 Probing for native availability of isel from userspace malc
2012-09-22 7:26 ` Segher Boessenkool
2012-09-22 10:12 ` malc
2012-09-22 10:21 ` Gabriel Paubert [this message]
2012-09-22 15:37 ` malc
2012-09-22 16:13 ` David Gibson
2012-09-22 19:08 ` Segher Boessenkool
2012-09-22 19:55 ` Benjamin Herrenschmidt
2012-09-22 20:17 ` malc
2012-09-23 1:46 ` Segher Boessenkool
2012-09-24 7:55 ` Gabriel Paubert
2012-09-24 7:58 ` Benjamin Herrenschmidt
2012-09-24 8:06 ` Gabriel Paubert
2012-09-24 9:41 ` Benjamin Herrenschmidt
2012-09-25 13:17 ` Segher Boessenkool
2012-09-25 20:59 ` Benjamin Herrenschmidt
2012-09-26 0:17 ` Kumar Gala
2012-09-24 23:55 ` Scott Wood
2012-09-25 0:32 ` Benjamin Herrenschmidt
2012-09-25 0:40 ` Scott Wood
2012-09-25 0:47 ` malc
2012-09-25 0:50 ` Scott Wood
2012-09-25 13:31 ` Segher Boessenkool
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