From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Date: Wed, 03 Mar 2004 21:08:00 +0000 Subject: RE: [PATCH] more robust halt_light Message-Id: <1078348080.2480.64.camel@patsy.fc.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 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. 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 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