From: Nathan Lynch <nathanl@linux.ibm.com>
To: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
Michael Ellerman <mpe@ellerman.id.au>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Tyrel Datwyler <tyreld@linux.ibm.com>
Subject: Re: [PATCH v2 4/5] powerpc/sysfs: Show idle_purr and idle_spurr for every CPU
Date: Fri, 21 Feb 2020 10:50:12 -0600 [thread overview]
Message-ID: <87eeunubp7.fsf@linux.ibm.com> (raw)
In-Reply-To: <1582262314-8319-5-git-send-email-ego@linux.vnet.ibm.com>
"Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:
> diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> index 80a676d..5b4b450 100644
> --- a/arch/powerpc/kernel/sysfs.c
> +++ b/arch/powerpc/kernel/sysfs.c
> @@ -19,6 +19,7 @@
> #include <asm/smp.h>
> #include <asm/pmc.h>
> #include <asm/firmware.h>
> +#include <asm/idle.h>
> #include <asm/svm.h>
>
> #include "cacheinfo.h"
> @@ -733,6 +734,42 @@ static void create_svm_file(void)
> }
> #endif /* CONFIG_PPC_SVM */
>
> +static void read_idle_purr(void *val)
> +{
> + u64 *ret = (u64 *)val;
No cast from void* needed.
> +
> + *ret = read_this_idle_purr();
> +}
> +
> +static ssize_t idle_purr_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct cpu *cpu = container_of(dev, struct cpu, dev);
> + u64 val;
> +
> + smp_call_function_single(cpu->dev.id, read_idle_purr, &val, 1);
> + return sprintf(buf, "%llx\n", val);
> +}
> +static DEVICE_ATTR(idle_purr, 0400, idle_purr_show, NULL);
> +
> +static void read_idle_spurr(void *val)
> +{
> + u64 *ret = (u64 *)val;
> +
> + *ret = read_this_idle_spurr();
> +}
> +
> +static ssize_t idle_spurr_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct cpu *cpu = container_of(dev, struct cpu, dev);
> + u64 val;
> +
> + smp_call_function_single(cpu->dev.id, read_idle_spurr, &val, 1);
> + return sprintf(buf, "%llx\n", val);
> +}
> +static DEVICE_ATTR(idle_spurr, 0400, idle_spurr_show, NULL);
It's regrettable that we have to wake up potentially idle CPUs in order
to derive correct idle statistics for them, but I suppose the main user
(lparstat) of these interfaces already is causing this to happen by
polling the existing per-cpu purr and spurr attributes.
So now lparstat will incur at minimum four syscalls and four IPIs per
CPU per polling interval -- one for each of purr, spurr, idle_purr and
idle_spurr. Correct?
At some point it's going to make sense to batch sampling of remote CPUs'
SPRs.
> static int register_cpu_online(unsigned int cpu)
> {
> struct cpu *c = &per_cpu(cpu_devices, cpu);
> @@ -794,10 +831,15 @@ static int register_cpu_online(unsigned int cpu)
> if (!firmware_has_feature(FW_FEATURE_LPAR))
> add_write_permission_dev_attr(&dev_attr_purr);
> device_create_file(s, &dev_attr_purr);
> + if (firmware_has_feature(FW_FEATURE_LPAR))
> + device_create_file(s, &dev_attr_idle_purr);
> }
>
> - if (cpu_has_feature(CPU_FTR_SPURR))
> + if (cpu_has_feature(CPU_FTR_SPURR)) {
> device_create_file(s, &dev_attr_spurr);
> + if (firmware_has_feature(FW_FEATURE_LPAR))
> + device_create_file(s, &dev_attr_idle_spurr);
> + }
>
> if (cpu_has_feature(CPU_FTR_DSCR))
> device_create_file(s, &dev_attr_dscr);
> @@ -879,11 +921,17 @@ static int unregister_cpu_online(unsigned int cpu)
> if (cpu_has_feature(CPU_FTR_MMCRA))
> device_remove_file(s, &dev_attr_mmcra);
>
> - if (cpu_has_feature(CPU_FTR_PURR))
> + if (cpu_has_feature(CPU_FTR_PURR)) {
> device_remove_file(s, &dev_attr_purr);
> + if (firmware_has_feature(FW_FEATURE_LPAR))
> + device_remove_file(s, &dev_attr_idle_purr);
> + }
>
> - if (cpu_has_feature(CPU_FTR_SPURR))
> + if (cpu_has_feature(CPU_FTR_SPURR)) {
> device_remove_file(s, &dev_attr_spurr);
> + if (firmware_has_feature(FW_FEATURE_LPAR))
> + device_remove_file(s, &dev_attr_idle_spurr);
> + }
>
> if (cpu_has_feature(CPU_FTR_DSCR))
> device_remove_file(s, &dev_attr_dscr);
The cpu register/unregister stuff here looks correct.
next prev parent reply other threads:[~2020-02-21 16:50 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 5:18 [PATCH v2 0/5] Track and expose idle PURR and SPURR ticks Gautham R. Shenoy
2020-02-21 5:18 ` [PATCH v2 1/5] powerpc: Move idle_loop_prolog()/epilog() functions to header file Gautham R. Shenoy
2020-02-21 15:03 ` Nathan Lynch
2020-02-24 4:55 ` Gautham R Shenoy
2020-03-06 17:06 ` Nathan Lynch
2020-02-21 5:18 ` [PATCH v2 2/5] powerpc/idle: Add accessor function to always read latest idle PURR Gautham R. Shenoy
2020-02-21 5:18 ` [PATCH v2 3/5] powerpc/pseries: Account for SPURR ticks on idle CPUs Gautham R. Shenoy
2020-02-21 16:47 ` Nathan Lynch
2020-02-24 5:05 ` Gautham R Shenoy
2020-02-21 5:18 ` [PATCH v2 4/5] powerpc/sysfs: Show idle_purr and idle_spurr for every CPU Gautham R. Shenoy
2020-02-21 16:50 ` Nathan Lynch [this message]
2020-02-24 5:14 ` Gautham R Shenoy
2020-02-25 10:20 ` Naveen N. Rao
2020-03-06 17:03 ` Nathan Lynch
2020-03-06 17:35 ` Naveen N. Rao
2020-02-21 5:18 ` [PATCH v2 5/5] Documentation: Document sysfs interfaces purr, spurr, idle_purr, idle_spurr Gautham R. Shenoy
2020-02-21 16:55 ` Nathan Lynch
2020-02-24 5:15 ` Gautham R Shenoy
2020-02-24 4:17 ` [PATCH v2 0/5] Track and expose idle PURR and SPURR ticks Kamalesh Babulal
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