From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: rostedt <rostedt@goodmis.org>
Cc: Alexei Starovoitov <ast@fb.com>,
"David S. Miller" <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
netdev <netdev@vger.kernel.org>, kernel-team <kernel-team@fb.com>,
linux-api <linux-api@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH v7 bpf-next 06/10] tracepoint: compute num_args at build time
Date: Wed, 28 Mar 2018 15:47:56 -0400 (EDT) [thread overview]
Message-ID: <686218133.247.1522266476295.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20180328153819.654c1600@gandalf.local.home>
----- On Mar 28, 2018, at 3:38 PM, rostedt rostedt@goodmis.org wrote:
> On Wed, 28 Mar 2018 15:32:20 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>> -#define __DO_TRACE(tp, proto, args, cond, rcucheck) \
>> +#define __DO_TRACE(name, proto, args, cond, rcucheck) \
>> do { \
>> struct tracepoint_func *it_func_ptr; \
>> void *it_func; \
>> @@ -140,7 +140,7 @@ extern void syscall_unregfunc(void);
>> if (rcucheck) \
>> rcu_irq_enter_irqson(); \
>> rcu_read_lock_sched_notrace(); \
>> - it_func_ptr = rcu_dereference_sched((tp)->funcs); \
>> + it_func_ptr = rcu_dereference_sched(__trace_##name##_funcs); \
>
> What we lose in data size, we may make up for in text (which is even
> more important). This will remove a dereference in the hot path.
>
> I'll make a few builds and run size on the vmlinux images to see how
> this pans out.
I like the approach. If it passes testing, I think it's a valuable improvement
to lessen cache footprint of tracepoint when tracing is active.
Thanks!
Mathieu
>
> -- Steve
>
>
>> if (it_func_ptr) { \
> > do { \
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2018-03-28 19:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-28 2:10 [PATCH v7 bpf-next 00/10] bpf, tracing: introduce bpf raw tracepoints Alexei Starovoitov
2018-03-28 2:10 ` [PATCH v7 bpf-next 01/10] treewide: remove large struct-pass-by-value from tracepoint arguments Alexei Starovoitov
2018-03-28 2:10 ` [PATCH v7 bpf-next 02/10] net/mediatek: disambiguate mt76 vs mt7601u trace events Alexei Starovoitov
2018-03-28 2:10 ` [PATCH v7 bpf-next 03/10] net/mac802154: disambiguate mac80215 vs mac802154 " Alexei Starovoitov
2018-03-28 2:10 ` [PATCH v7 bpf-next 04/10] net/wireless/iwlwifi: fix iwlwifi_dev_ucode_error tracepoint Alexei Starovoitov
2018-03-28 2:11 ` [PATCH v7 bpf-next 05/10] macro: introduce COUNT_ARGS() macro Alexei Starovoitov
2018-03-28 2:11 ` [PATCH v7 bpf-next 06/10] tracepoint: compute num_args at build time Alexei Starovoitov
2018-03-28 13:49 ` Mathieu Desnoyers
2018-03-28 16:43 ` Alexei Starovoitov
2018-03-28 17:04 ` Steven Rostedt
2018-03-28 17:10 ` Alexei Starovoitov
2018-03-28 17:38 ` Steven Rostedt
2018-03-28 18:03 ` Alexei Starovoitov
2018-03-28 18:10 ` Steven Rostedt
2018-03-28 18:19 ` Alexei Starovoitov
2018-03-28 18:54 ` Steven Rostedt
2018-03-28 19:22 ` Mathieu Desnoyers
2018-03-28 19:25 ` Alexei Starovoitov
2018-03-28 19:32 ` Steven Rostedt
2018-03-28 19:38 ` Steven Rostedt
2018-03-28 19:47 ` Mathieu Desnoyers [this message]
2018-03-28 17:14 ` Mathieu Desnoyers
2018-03-28 2:11 ` [PATCH v7 bpf-next 07/10] bpf: introduce BPF_RAW_TRACEPOINT Alexei Starovoitov
2018-03-28 17:41 ` Steven Rostedt
2018-03-28 2:11 ` [PATCH v7 bpf-next 08/10] libbpf: add bpf_raw_tracepoint_open helper Alexei Starovoitov
2018-03-28 2:11 ` [PATCH v7 bpf-next 09/10] samples/bpf: raw tracepoint test Alexei Starovoitov
2018-03-28 2:11 ` [PATCH v7 bpf-next 10/10] selftests/bpf: test for bpf_get_stackid() from raw tracepoints Alexei Starovoitov
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