linux/arch/x86/kernel/cpu
Huang Rui b466bdb614 x86/asm/delay: Introduce an MWAITX-based delay with a configurable timer
MWAITX can enable a timer and a corresponding timer value
specified in SW P0 clocks. The SW P0 frequency is the same as
TSC. The timer provides an upper bound on how long the
instruction waits before exiting.

This way, a delay function in the kernel can leverage that
MWAITX timer of MWAITX.

When a CPU core executes MWAITX, it will be quiesced in a
waiting phase, diminishing its power consumption. This way, we
can save power in comparison to our default TSC-based delays.

A simple test shows that:

	$ cat /sys/bus/pci/devices/0000\:00\:18.4/hwmon/hwmon0/power1_acc
	$ sleep 10000s
	$ cat /sys/bus/pci/devices/0000\:00\:18.4/hwmon/hwmon0/power1_acc

Results:

	* TSC-based default delay:      485115 uWatts average power
	* MWAITX-based delay:           252738 uWatts average power

Thus, that's about 240 milliWatts less power consumption. The
test method relies on the support of AMD CPU accumulated power
algorithm in fam15h_power for which patches are forthcoming.

Suggested-by: Andy Lutomirski <luto@amacapital.net>
Suggested-by: Borislav Petkov <bp@suse.de>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Huang Rui <ray.huang@amd.com>
[ Fix delay truncation. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Andreas Herrmann <herrmann.der.user@gmail.com>
Cc: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Hector Marco-Gisbert <hecmargi@upv.es>
Cc: Jacob Shin <jacob.w.shin@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Li <tony.li@amd.com>
Link: http://lkml.kernel.org/r/1438744732-1459-3-git-send-email-ray.huang@amd.com
Link: http://lkml.kernel.org/r/1439201994-28067-4-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-08-22 14:52:16 +02:00
..
mcheck x86/entry: Remove exception_enter() from most trap handlers 2015-07-07 10:59:09 +02:00
microcode x86/microcode: Correct CPU family related variable types 2015-06-07 15:38:15 +02:00
mtrr x86/mm/pat: Wrap pat_enabled into a function API 2015-05-27 14:41:01 +02:00
.gitignore
amd.c x86/asm/delay: Introduce an MWAITX-based delay with a configurable timer 2015-08-22 14:52:16 +02:00
bugs_64.c
bugs.c x86/fpu: Move various internal function prototypes to fpu/internal.h 2015-05-19 15:47:48 +02:00
centaur.c x86: Remove CONFIG_X86_OOSTORE 2014-03-11 10:16:18 -07:00
common.c x86/ldt: Make modify_ldt synchronous 2015-07-31 10:23:23 +02:00
cpu.h x86/cpu: Track legacy CPU model data only on 32-bit kernels 2013-10-26 13:34:39 +02:00
cyrix.c x86: Delete non-required instances of include <linux/init.h> 2014-01-06 21:25:18 -08:00
hypervisor.c hypervisor/x86/xen: Unset X86_BUG_SYSRET_SS_ATTRS on Xen PV guests 2015-05-05 18:27:43 +01:00
intel_cacheinfo.c x86: Kill CONFIG_X86_HT 2015-06-07 15:33:44 +02:00
intel_pt.h perf/x86/intel/pt: Add Intel PT PMU driver 2015-04-02 17:14:20 +02:00
intel.c x86/cpu/intel: Fix trivial typo in intel_tlb_table[] 2015-02-22 08:55:58 +01:00
Makefile perf/x86/intel/bts: Add BTS PMU driver 2015-04-02 17:14:21 +02:00
match.c x86: align x86 arch with generic CPU modalias handling 2014-02-18 12:45:38 -08:00
mkcapflags.sh x86/build: Fix mkcapflags.sh bash-ism 2015-02-19 02:21:00 +01:00
mshyperv.c x86: Use entering[_ack]_irq() instead of open coding it 2015-05-15 16:03:18 +02:00
perf_event_amd_ibs.c perf/x86/amd/ibs: Convert force_ibs_eilvt_setup() to void 2015-02-18 17:01:46 +01:00
perf_event_amd_iommu.c cpumask: factor out show_cpumap into separate helper function 2014-11-07 11:45:00 -08:00
perf_event_amd_iommu.h
perf_event_amd_uncore.c cpumask: factor out show_cpumap into separate helper function 2014-11-07 11:45:00 -08:00
perf_event_amd.c perf/x86: Add 'index' param to get_event_constraint() callback 2015-04-02 17:33:10 +02:00
perf_event_intel_bts.c Replace module_init with appropriate alternate initcall in non modules. 2015-07-02 10:36:29 -07:00
perf_event_intel_cqm.c perf/x86/intel/cqm: Do not access cpu_data() from CPU_UP_PREPARE handler 2015-08-12 11:37:23 +02:00
perf_event_intel_ds.c perf/x86/intel/pebs: Add PEBSv3 decoding 2015-06-07 16:09:16 +02:00
perf_event_intel_lbr.c perf/x86/intel: Drain the PEBS buffer during context switches 2015-06-07 16:08:54 +02:00
perf_event_intel_pt.c Replace module_init with appropriate alternate initcall in non modules. 2015-07-02 10:36:29 -07:00
perf_event_intel_rapl.c Merge branch 'linus' into timers/core 2015-05-19 16:12:32 +02:00
perf_event_intel_uncore_nhmex.c perf/x86/uncore: Fix coccinelle warnings 2014-08-13 07:51:09 +02:00
perf_event_intel_uncore_snb.c perf/x86/intel/uncore: Add Broadwell-U uncore IMC PMU support 2015-05-11 11:57:47 +02:00
perf_event_intel_uncore_snbep.c perf/x86/intel/uncore: Fix CBOX bit wide and UBOX reg on Haswell-EP 2015-06-07 15:46:50 +02:00
perf_event_intel_uncore.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-06-22 18:57:44 -07:00
perf_event_intel_uncore.h Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-06-22 15:19:21 -07:00
perf_event_intel.c perf/x86/intel: Fix memory leak on hot-plug allocation fail 2015-08-12 11:37:22 +02:00
perf_event_knc.c x86: Replace __get_cpu_var uses 2014-08-26 13:45:49 -04:00
perf_event_p4.c x86: Replace __get_cpu_var uses 2014-08-26 13:45:49 -04:00
perf_event_p6.c perf/x86/intel/p6: Add userspace RDPMC quirk for PPro 2014-02-09 13:08:24 +01:00
perf_event.c x86/ldt: Make modify_ldt() optional 2015-07-31 13:30:45 +02:00
perf_event.h Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-06-22 15:45:41 -07:00
perfctr-watchdog.c
powerflags.c
proc.c x86: Replace cpu_**_mask() with topology_**_cpumask() 2015-05-27 15:22:17 +02:00
rdrand.c x86, rdrand: When nordrand is specified, disable RDSEED as well 2014-05-11 20:25:20 -07:00
scattered.c x86: Add Intel Processor Trace (INTEL_PT) cpu feature detection 2015-04-02 17:14:18 +02:00
topology.c
transmeta.c x86: Delete non-required instances of include <linux/init.h> 2014-01-06 21:25:18 -08:00
umc.c x86: Delete non-required instances of include <linux/init.h> 2014-01-06 21:25:18 -08:00
vmware.c