From: Valentin Schneider <vschneid@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org,
linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org,
loongarch@lists.linux.dev, linux-mips@vger.kernel.org,
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linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
x86@kernel.org, Steven Rostedt <rostedt@goodmis.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Russell King <linux@armlinux.org.uk>,
Nicholas Piggin <npiggin@gmail.com>, Guo Ren <guoren@kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v5 1/7] trace: Add trace_ipi_send_cpumask()
Date: Wed, 22 Mar 2023 11:24:53 +0000 [thread overview]
Message-ID: <xhsmhpm91c9kq.mognet@vschneid.remote.csb> (raw)
In-Reply-To: <20230322103004.GA571242@hirez.programming.kicks-ass.net>
On 22/03/23 11:30, Peter Zijlstra wrote:
> On Wed, Mar 22, 2023 at 10:39:55AM +0100, Peter Zijlstra wrote:
>> On Tue, Mar 07, 2023 at 02:35:52PM +0000, Valentin Schneider wrote:
>> > +TRACE_EVENT(ipi_send_cpumask,
>> > +
>> > + TP_PROTO(const struct cpumask *cpumask, unsigned long callsite, void *callback),
>> > +
>> > + TP_ARGS(cpumask, callsite, callback),
>> > +
>> > + TP_STRUCT__entry(
>> > + __cpumask(cpumask)
>> > + __field(void *, callsite)
>> > + __field(void *, callback)
>> > + ),
>> > +
>> > + TP_fast_assign(
>> > + __assign_cpumask(cpumask, cpumask_bits(cpumask));
>> > + __entry->callsite = (void *)callsite;
>> > + __entry->callback = callback;
>> > + ),
>> > +
>> > + TP_printk("cpumask=%s callsite=%pS callback=%pS",
>> > + __get_cpumask(cpumask), __entry->callsite, __entry->callback)
>> > +);
>>
>> Would it make sense to add a variant like: ipi_send_cpu() that records a
>> single cpu instead of a cpumask. A lot of sites seems to do:
>> cpumask_of(cpu) for that first argument, and it seems to me it is quite
>> daft to have to memcpy a full multi-word cpumask in those cases.
>>
>> Remember, nr_possible_cpus > 64 is quite common these days.
>
> Something we litte bit like so...
>
I was wondering whether we could stick with a single trace event, but let
ftrace be aware of weight=1 vs weight>1 cpumasks.
For weight>1, it would memcpy() as usual, for weight=1, it could write a
pointer to a cpu_bit_bitmap[] equivalent embedded in the trace itself.
Unfortunately, Ftrace bitmasks are represented as a u32 made of two 16 bit
values: [offset in event record, size], so there isn't a straightforward
way to point to a "reusable" cpumask. AFAICT the only alternative would be
to do that via a different trace event, but then we should just go with a
plain old uint - i.e. do what you're doing here, so:
Tested-and-reviewed-by: Valentin Schneider <vschneid@redhat.com>
(with the tiny typo fix below)
> @@ -35,6 +35,28 @@ TRACE_EVENT(ipi_raise,
> TP_printk("target_mask=%s (%s)", __get_bitmask(target_cpus), __entry->reason)
> );
>
> +TRACE_EVENT(ipi_send_cpu,
> +
> + TP_PROTO(const unsigned int cpu, unsigned long callsite, void *callback),
> +
> + TP_ARGS(cpu, callsite, callback),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, cpu)
> + __field(void *, callsite)
> + __field(void *, callback)
> + ),
> +
> + TP_fast_assign(
> + __entry->cpu = cpu;
> + __entry->callsite = (void *)callsite;
> + __entry->callback = callback;
> + ),
> +
> + TP_printk("cpu=%s callsite=%pS callback=%pS",
^
s/s/u/
> + __entry->cpu, __entry->callsite, __entry->callback)
> +);
> +
next prev parent reply other threads:[~2023-03-22 11:25 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-07 14:35 [PATCH v5 0/7] Generic IPI sending tracepoint Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 1/7] trace: Add trace_ipi_send_cpumask() Valentin Schneider
2023-03-22 9:39 ` Peter Zijlstra
2023-03-22 10:30 ` Peter Zijlstra
2023-03-22 11:24 ` Valentin Schneider [this message]
2023-03-07 14:35 ` [PATCH v5 2/7] sched, smp: Trace IPIs sent via send_call_function_single_ipi() Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 3/7] smp: Trace IPIs sent via arch_send_call_function_ipi_mask() Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 4/7] irq_work: Trace self-IPIs sent via arch_irq_work_raise() Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 5/7] treewide: Trace IPIs sent via smp_send_reschedule() Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 6/7] smp: reword smp call IPI comment Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 7/7] sched, smp: Trace smp callback causing an IPI Valentin Schneider
2023-03-22 9:53 ` Peter Zijlstra
2023-03-22 12:20 ` Valentin Schneider
2023-03-22 14:04 ` Peter Zijlstra
2023-03-22 17:01 ` Valentin Schneider
2023-03-22 17:22 ` Peter Zijlstra
2023-03-22 18:22 ` Valentin Schneider
2023-03-22 23:14 ` Peter Zijlstra
2023-03-23 16:25 ` Valentin Schneider
2023-03-23 17:41 ` Peter Zijlstra
2023-03-23 18:31 ` Valentin Schneider
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