From: Nathan Lynch <nathanl@linux.ibm.com>
To: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.ibm.com>,
linux-kernel@vger.kernel.org,
Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 3/5] powerpc/pseries: Account for SPURR ticks on idle CPUs
Date: Fri, 21 Feb 2020 10:47:41 -0600 [thread overview]
Message-ID: <87ftf3ubte.fsf@linux.ibm.com> (raw)
In-Reply-To: <1582262314-8319-4-git-send-email-ego@linux.vnet.ibm.com>
"Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes:
> +static inline void snapshot_spurr_idle_entry(void)
> +{
> + *this_cpu_ptr(&idle_entry_spurr_snap) = mfspr(SPRN_SPURR);
> +}
> +
[...]
> +static inline void update_idle_spurr_accounting(void)
> +{
> + u64 *idle_spurr_cycles_ptr = this_cpu_ptr(&idle_spurr_cycles);
> + u64 in_spurr = *this_cpu_ptr(&idle_entry_spurr_snap);
> +
> + *idle_spurr_cycles_ptr += mfspr(SPRN_SPURR) - in_spurr;
> +}
[...]
> +static inline u64 read_this_idle_spurr(void)
> +{
> + /*
> + * If we are reading from an idle context, update the
> + * idle-spurr cycles corresponding to the last idle period.
> + * Since the idle context is not yet over, take a fresh
> + * snapshot of the idle-spurr.
> + */
> + if (get_lppaca()->idle == 1) {
> + update_idle_spurr_accounting();
> + snapshot_spurr_idle_entry();
This samples spurr twice when it could do with just one. I don't know
the performance implications, but will the results be coherent?
next prev parent reply other threads:[~2020-02-21 16:49 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 [this message]
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
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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