Mike, > -----Original Message----- > From: Turquette, Mike [mailto:mturquette@xxxxxx] > Sent: Wednesday, December 01, 2010 1:20 AM > To: Vishwanath BS > Cc: linux-omap@xxxxxxxxxxxxxxx; linaro-dev@xxxxxxxxxxxxxxxx > Subject: Re: [PATCH] OMAP PM: Optimize cpufreq transition latency > > On Thu, Nov 25, 2010 at 7:38 AM, Vishwanath BS > <vishwanath.bs@xxxxxx> wrote: > > Currently cpufreq transition latency value does not really reflect the > actual > > OMAP OPP transition delay. This patch has the actual latency value. > > I did profile the DVFS latency on OMAP3430, OMAP3630 and OMAP4 > for worstcase(MPU and Core together) and found that in none of these > platforms, transiton value > > goes beyong 10ms. Added a buffer of 20ms to avoid too frequent > ondemand timer > > expiry. > > With this change, performance of ondemand governor is improved > when tested > > using cpufreqbench tool. Without this patch, cpufreq-bench reported > ondemand > > performance as 40% of performance governor, and with this patch it's > around 70% > > (using below procedure). > > > > cpufreq-bench: > > http://lwn.net/Articles/339862/ > > http://ftp.riken.go.jp/archives/Linux/suse/people/ckornacker/cpufreq- > bench/ > > > > Command used for performance testing: > > cpufreq-bench -l 50000 -s 100000 -x 50000 -y 100000 -g ondemand - > r 5 -n 5 -v > > > > Signed-off-by: Vishwanath BS <vishwanath.bs@xxxxxx> > > --- > > arch/arm/plat-omap/cpu-omap.c | 4 ++-- > > 1 files changed, 2 insertions(+), 2 deletions(-) > > mode change 100644 => 100755 arch/arm/plat-omap/cpu-omap.c > > > > diff --git a/arch/arm/plat-omap/cpu-omap.c b/arch/arm/plat- > omap/cpu-omap.c > > old mode 100644 > > new mode 100755 > > index c47faf8..d3fc423 > > --- a/arch/arm/plat-omap/cpu-omap.c > > +++ b/arch/arm/plat-omap/cpu-omap.c > > @@ -158,8 +158,8 @@ static int __init omap_cpu_init(struct > cpufreq_policy *policy) > > policy->max = policy->cpuinfo.max_freq; > > policy->cur = omap_getspeed(0); > > > > - /* FIXME: what's the actual transition time? */ > > - policy->cpuinfo.transition_latency = 300 * 1000; > > + /* Program the actual transition time for worstcase */ > > + policy->cpuinfo.transition_latency = 30 * 1000; > > Vishwa, > > This is a frequent periodic timer. Does a smaller value have any > affect on CPUidle wakeups? I do not think so since this is a deferrable timer which should not interrupt CPUIdle. Vishwa > > Thanks, > Mike > > > return 0; > > } > > -- > > 1.7.0.4 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
