Re: [PATCH v8 3/6] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path
flat view
From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: 2016-03-18 13:14:04
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linux-pm, lkml
On Fri, Mar 18, 2016 at 5:11 AM, Michael Neuling [off-list ref] wrote:
On Fri, 2016-03-18 at 15:04 +1100, Michael Neuling wrote:quoted
On Wed, 2016-02-03 at 01:11 +0530, Shilpasri G Bhat wrote:quoted
quoted
cpu_to_chip_id() does a DT walk through to find out the chip id by taking a contended device tree lock. This adds an unnecessary overhead in a hot path. So instead of calling cpu_to_chip_id() everytime cache the chip ids for all cores in the array 'core_to_chip_map' and use it in the hotpath. Reported-by: Anton Blanchard <redacted> Signed-off-by: Shilpasri G Bhat <redacted> Reviewed-by: Gautham R. Shenoy <redacted> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> --- No changes from v7.How about this instead? It removes the linear lookup and seems a lot less complex.
This has gone in already. Can you please send a patch on top of it?
quoted hunk ↗ jump to hunk
BTW we never init nr_chips before using it. We also need something like.diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index d63d2cb..c819ed4 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c@@ -556,6 +556,8 @@ static int init_chip_info(void) unsigned int cpu, i; unsigned int prev_chip_id = UINT_MAX; + nr_chips = 0; + for_each_possible_cpu(cpu) { unsigned int id = cpu_to_chip_id(cpu);
Including this part too maybe? Thanks, Rafael