linux-kernel - Re: [PATCH v3 0/2] cpufreq: powernv: Ramp-down global pstate slower than local-pstate

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Date:	Wed, 04 May 2016 23:17:14 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>
Cc:	viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	ego@...ux.vnet.ibm.com
Subject: Re: [PATCH v3 0/2]  cpufreq: powernv: Ramp-down global pstate slower than local-pstate

On Tuesday, April 19, 2016 03:27:59 PM Akshay Adiga wrote:
> The frequency transition latency from pmin to pmax is observed to be in few
> millisecond granurality. And it usually happens to take a performance penalty
> during sudden frequency rampup requests.
> 
> This patch set solves this problem by using a chip-level entity called "global
> pstates". Global pstate manages elements across other dependent core chiplets.
> Typically, the element that needs to be managed is the voltage setting.
> So by holding global pstates higher than local pstate for some amount of time
> ( ~5 seconds) the subsequent rampups could be made faster.
> 
> (1/2) patch removes the flag from cpufreq_policy->driver_data, so that it can
> be used for tracking global pstates.
> 
> (2/2) patch adds code for global pstate management.
> - The iozone results with this patchset, shows improvements in almost all cases.
> - YCSB workload on redis with various  target operations per second shows 
> better MaxLatency with this patch.
> 
> Changes from v1:
> - Fixed coding style
> - Added a routine to reset global_pstate_info instead of hacky memset
> - Handled case where cpufreq_table_validate_and_show() fails
> - changed int queue_gpstate_timer() to void queue_gpstate_timer()
> 
> Changes from v2:
> - dropped the unreated change. 
> 
> Akshay Adiga (1):
>   cpufreq: powernv: Ramp-down global pstate slower than local-pstate
> 
> Shilpasri G Bhat (1):
>   cpufreq: powernv: Remove flag use-case of policy->driver_data
> 
>  drivers/cpufreq/powernv-cpufreq.c | 269 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 256 insertions(+), 13 deletions(-)

Both [1-2/2] applied, thanks!