From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Grundler Date: Wed, 03 Mar 2004 23:35:27 +0000 Subject: Re: [PATCH] more robust halt_light Message-Id: <20040303233527.GP27501@cup.hp.com> List-Id: References: <1078336640.2480.37.camel@patsy.fc.hp.com> In-Reply-To: <1078336640.2480.37.camel@patsy.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Wed, Mar 03, 2004 at 02:08:00PM -0700, Alex Williamson wrote: > > I was curious about that myself, but I thought I remembered from > Stephane that the perf counters didn't really recover from a > PAL_HALT_LIGHT on McKinley. The way I recall Stephane explaining it to me was the PMU was completely disabled after returning from PAL_HALT_LIGHT. ISTR no PAL fix was never released for Mckinley. And even if one was, we'd have to convince HP firmware teams to roll and qualify it. Unlikely. > If that's not the case, maybe we can move > the PAL check into perfmon code, and it can selectively disable it as it > needs via the disable_hlt API. I don't think that's likely...but poke stephane again when he's back. But I do like rohit's idea that perfmon enable/disable PAL_HALT when it starts/stops using the PMU. grant > I assume there are some cases were > perfmon wouldn't need to disable halt_light on working PAL, > so the rev check might not go away. > > Alex > > On Wed, 2004-03-03 at 13:38, Seth, Rohit wrote: > > The issue with performance counters is only when PAL_HALT_LIGHT is > > enabled. It is nice to be able to use this power save feature when the > > performance counters are not currently/actively used system wide. Can > > we use the disable_hlt and enable_hlt APIs (mentioned in the patch > > below) in perfmon kind of tools to disable/enable PAL_HALT_LIGHT > > whenever the system is transitioning in and out of system wide > > performance monitoring. That way we don't have to have any tests for > > Mckinley, PAL versions etc. etc. > > > > rohit > > >-----Original Message----- > > >Sent: Wednesday, March 03, 2004 9:57 AM > > >To: linux-ia64@vger.kernel.org > > >Subject: [PATCH] more robust halt_light > > > > > > > > > This patch adds some i386-ish enable/disable features to the > > >pal_halt_light cpu idle implementation as well as tries to avoid bad > > >interactions with certain revs of PAL on McKinley cpus. Hopefully this > > >will provide enough flexibility that we can leave it configured on in > > >the kernel by default. My latest measurements on a 1.3GHz rx2600 show > > >that enabling pal_halt_light in the cpu_idle routine saves 23W/cpu on > > an > > >idle system. > > > > > > FWIW, I added the enable/disable_hlt routines. I don't see any > > >consumers of this for ia64 now, but it looked useful. Patch against > > >latest linux-2.5 bk. Thanks, > > > > > > Alex > > > > > -- > Alex Williamson HP Linux & Open Source Lab > > - > To unsubscribe from this list: send the line "unsubscribe linux-ia64" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html