From: "Hunt, David" <david.hunt@intel.com>
To: Markus Theil <markus.theil@tu-ilmenau.de>
Cc: <dev@dpdk.org>
Subject: Re: [PATCH] power: add unpriv. read of turbo % for pstate
Date: Thu, 25 Aug 2022 16:09:31 +0100 [thread overview]
Message-ID: <cb812f24-5388-734c-422c-efd3c9602a47@intel.com> (raw)
In-Reply-To: <20220824192859.66095-1-markus.theil@tu-ilmenau.de>
Hi Markus,
On 24/08/2022 20:28, Markus Theil wrote:
> If DPDK applications should be used with a minimal set of privileges,
> using the msr kernel module on linux should not be necessary.
>
> Since at least kernel 4.4 the rdmsr call to obtain the last non-turbo
> boost frequency can be left out, if the sysfs interface is used.
> Also RHEL 7 with recent kernel updates should include the sysfs interface
> for this (I only looked this up for CentOS 7).
>
> Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>
> ---
> lib/power/power_pstate_cpufreq.c | 69 ++++++++++++++++++--------------
> 1 file changed, 40 insertions(+), 29 deletions(-)
>
> diff --git a/lib/power/power_pstate_cpufreq.c b/lib/power/power_pstate_cpufreq.c
> index 78c9197695..c3d66a8f68 100644
> --- a/lib/power/power_pstate_cpufreq.c
> +++ b/lib/power/power_pstate_cpufreq.c
> @@ -35,15 +35,9 @@
> "/sys/devices/system/cpu/cpu%u/cpufreq/cpuinfo_min_freq"
> #define POWER_SYSFILE_BASE_FREQ \
> "/sys/devices/system/cpu/cpu%u/cpufreq/base_frequency"
> +#define POWER_SYSFILE_TURBO_PCT \
> + "/sys/devices/system/cpu/intel_pstate/turbo_pct"
> #define POWER_PSTATE_DRIVER "intel_pstate"
> -#define POWER_MSR_PATH "/dev/cpu/%u/msr"
> -
> -/*
> - * MSR related
> - */
> -#define PLATFORM_INFO 0x0CE
> -#define NON_TURBO_MASK 0xFF00
> -#define NON_TURBO_OFFSET 0x8
>
>
> enum power_state {
> @@ -74,37 +68,33 @@ struct pstate_power_info {
> static struct pstate_power_info lcore_power_info[RTE_MAX_LCORE];
>
> /**
> - * It is to read the specific MSR.
> + * It is to read the turbo mode percentage from sysfs
> */
> -
> static int32_t
> -power_rdmsr(int msr, uint64_t *val, unsigned int lcore_id)
> +power_read_turbo_pct(uint64_t *outVal)
> {
> int fd, ret;
> - char fullpath[PATH_MAX];
> + char val[4] = {0};
>
> - snprintf(fullpath, sizeof(fullpath), POWER_MSR_PATH, lcore_id);
> -
> - fd = open(fullpath, O_RDONLY);
> + fd = open(POWER_SYSFILE_TURBO_PCT, O_RDONLY);
>
> if (fd < 0) {
> - RTE_LOG(ERR, POWER, "Error opening '%s': %s\n", fullpath,
> + RTE_LOG(ERR, POWER, "Error opening '%s': %s\n", POWER_SYSFILE_TURBO_PCT,
> strerror(errno));
> return fd;
> }
>
> - ret = pread(fd, val, sizeof(uint64_t), msr);
> + ret = read(fd, val, sizeof(val));
>
> if (ret < 0) {
> - RTE_LOG(ERR, POWER, "Error reading '%s': %s\n", fullpath,
> + RTE_LOG(ERR, POWER, "Error reading '%s': %s\n", POWER_SYSFILE_TURBO_PCT,
> strerror(errno));
> goto out;
> }
>
> - POWER_DEBUG_TRACE("MSR Path %s, offset 0x%X for lcore %u\n",
> - fullpath, msr, lcore_id);
> + *outVal = (uint64_t) atol(val);
>
I'd recommend replacing atol with strtol, it's a safer implementation.
It's more commonly found in DPDK code than atol.
> - POWER_DEBUG_TRACE("Ret value %d, content is 0x%"PRIx64"\n", ret, *val);
> + POWER_DEBUG_TRACE("power turbo pct: %"PRIu64"\n", *outVal);
>
> out: close(fd);
> return ret;
> @@ -116,8 +106,9 @@ out: close(fd);
> static int
> power_init_for_setting_freq(struct pstate_power_info *pi)
> {
> - FILE *f_base = NULL, *f_base_max = NULL, *f_min = NULL, *f_max = NULL;
> - uint32_t base_ratio, base_max_ratio;
> + FILE *f_base = NULL, *f_base_min = NULL, *f_base_max = NULL,
> + *f_min = NULL, *f_max = NULL;
> + uint32_t base_ratio, base_min_ratio, base_max_ratio;
> uint64_t max_non_turbo;
> int ret;
>
> @@ -130,6 +121,14 @@ power_init_for_setting_freq(struct pstate_power_info *pi)
> goto err;
> }
>
> + open_core_sysfs_file(&f_base_min, "r", POWER_SYSFILE_BASE_MIN_FREQ,
> + pi->lcore_id);
> + if (f_base_min == NULL) {
> + RTE_LOG(ERR, POWER, "failed to open %s\n",
> + POWER_SYSFILE_BASE_MIN_FREQ);
> + goto err;
> + }
> +
> open_core_sysfs_file(&f_min, "rw+", POWER_SYSFILE_MIN_FREQ,
> pi->lcore_id);
> if (f_min == NULL) {
> @@ -158,6 +157,14 @@ power_init_for_setting_freq(struct pstate_power_info *pi)
> goto err;
> }
>
> + /* read base min ratio */
> + ret = read_core_sysfs_u32(f_base_min, &base_min_ratio);
> + if (ret < 0) {
> + RTE_LOG(ERR, POWER, "Failed to read %s\n",
> + POWER_SYSFILE_BASE_MIN_FREQ);
> + goto err;
> + }
> +
> /* base ratio may not exist */
> if (f_base != NULL) {
> ret = read_core_sysfs_u32(f_base, &base_ratio);
> @@ -170,20 +177,22 @@ power_init_for_setting_freq(struct pstate_power_info *pi)
> base_ratio = 0;
> }
>
> - /* Add MSR read to detect turbo status */
> - if (power_rdmsr(PLATFORM_INFO, &max_non_turbo, pi->lcore_id) < 0)
> - goto err;
> - /* no errors after this point */
> -
> /* convert ratios to bins */
> base_max_ratio /= BUS_FREQ;
> + base_min_ratio /= BUS_FREQ;
> base_ratio /= BUS_FREQ;
>
> /* assign file handles */
> pi->f_cur_min = f_min;
> pi->f_cur_max = f_max;
>
> - max_non_turbo = (max_non_turbo&NON_TURBO_MASK)>>NON_TURBO_OFFSET;
> + /* try to get turbo from global sysfs entry for less privileges than from MSR */
> + if (power_read_turbo_pct(&max_non_turbo) < 0)
> + goto err;
> + /* no errors after this point */
> +
> + max_non_turbo = base_min_ratio
> + + (100 - max_non_turbo) * (base_max_ratio - base_min_ratio) / 100;
>
> POWER_DEBUG_TRACE("no turbo perf %"PRIu64"\n", max_non_turbo);
>
> @@ -220,6 +229,8 @@ power_init_for_setting_freq(struct pstate_power_info *pi)
> err:
> if (f_base != NULL)
> fclose(f_base);
> + if (f_base_min != NULL)
> + fclose(f_base_min);
> if (f_base_max != NULL)
> fclose(f_base_max);
> if (f_min != NULL)
Nice patch.
I've run the patched code and can confirm that the max_non_turbo value
agrees with the relevant byte in the 0xCE MSR, so looks good.
Tested-By: David Hunt <david.hunt@intel.com>
Also, once the atol issue mentioned above is resolved:
Acked-By: David Hunt <david.hunt@intel.com>
Thanks!
next prev parent reply other threads:[~2022-08-25 15:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-24 19:28 Markus Theil
2022-08-25 15:09 ` Hunt, David [this message]
2022-08-25 18:22 ` [PATCH v2] " Markus Theil
2022-10-10 0:54 ` Thomas Monjalon
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