From: Peter Zijlstra <peterz@infradead.org>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
David Ahern <dsahern@gmail.com>, Andi Kleen <ak@linux.intel.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>
Subject: Re: [PATCH 06/12] perf: Return empty callchain instead of NULL
Date: Mon, 8 Jan 2018 13:15:16 +0100 [thread overview]
Message-ID: <20180108121516.GJ3040@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180107160356.28203-7-jolsa@kernel.org>
On Sun, Jan 07, 2018 at 05:03:50PM +0100, Jiri Olsa wrote:
> It simplifies the code a bit, because we dump the callchain
> even if it's empty. With 'empty' callchain we can remove
> all the NULL-checking code paths.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> Original-patch-from: Peter Zijlstra <peterz@infradead.org>
> Link: http://lkml.kernel.org/n/tip-n4t869o2qc1b31v4wwvmxznb@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> kernel/events/core.c | 30 ++++++++++++------------------
> 1 file changed, 12 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 5fc1ded4b450..4e1a1bf8d867 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5815,19 +5815,11 @@ void perf_output_sample(struct perf_output_handle *handle,
> perf_output_read(handle, event);
>
> if (sample_type & PERF_SAMPLE_CALLCHAIN) {
> - if (data->callchain) {
> - int size = 1;
> -
> - if (data->callchain)
> - size += data->callchain->nr;
> -
> - size *= sizeof(u64);
> + int size = 1;
>
> - __output_copy(handle, data->callchain, size);
> - } else {
> - u64 nr = 0;
> - perf_output_put(handle, nr);
> - }
> + size += data->callchain->nr;
> + size *= sizeof(u64);
> + __output_copy(handle, data->callchain, size);
> }
>
> if (sample_type & PERF_SAMPLE_RAW) {
> @@ -5980,6 +5972,8 @@ static u64 perf_virt_to_phys(u64 virt)
> return phys_addr;
> }
>
> +static struct perf_callchain_entry __empty_callchain = { .nr = 0, };
> +
> static struct perf_callchain_entry *
> perf_callchain(struct perf_event *event, struct pt_regs *regs)
> {
> @@ -5988,12 +5982,14 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
> /* Disallow cross-task user callchains. */
> bool crosstask = event->ctx->task && event->ctx->task != current;
> const u32 max_stack = event->attr.sample_max_stack;
> + struct perf_callchain_entry *callchain;
>
> if (!kernel && !user)
> - return NULL;
> + return &__empty_callchain;
>
> - return get_perf_callchain(regs, 0, kernel, user,
> - max_stack, crosstask, true);
> + callchain = get_perf_callchain(regs, 0, kernel, user,
> + max_stack, crosstask, true);
> + return callchain ?: &__empty_callchain;
> }
>
> void perf_prepare_sample(struct perf_event_header *header,
> @@ -6018,9 +6014,7 @@ void perf_prepare_sample(struct perf_event_header *header,
> int size = 1;
>
> data->callchain = perf_callchain(event, regs);
> -
> - if (data->callchain)
> - size += data->callchain->nr;
> + size += data->callchain->nr;
>
> header->size += size * sizeof(u64);
> }
> --
> 2.13.6
>
next prev parent reply other threads:[~2018-01-08 12:15 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-07 16:03 [PATCH 00/12] perf: Assorted fixes Jiri Olsa
2018-01-07 16:03 ` [PATCH 01/12] perf tools: Enable LIBBABELTRACE by default Jiri Olsa
2018-01-08 15:17 ` Arnaldo Carvalho de Melo
2018-01-08 15:20 ` Arnaldo Carvalho de Melo
2018-01-08 15:24 ` Arnaldo Carvalho de Melo
2018-01-08 17:11 ` Jiri Olsa
2018-01-08 17:16 ` Jiri Olsa
2018-01-09 9:26 ` [PATCH] perf build: Display EXTRA features for VF=1 build Jiri Olsa
2018-01-19 10:15 ` Jiri Olsa
2018-01-19 12:43 ` Arnaldo Carvalho de Melo
2018-01-24 11:23 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-11 6:24 ` [tip:perf/core] perf tools: Enable LIBBABELTRACE by default tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 02/12] perf tools: Display perf_event_attr::namespaces debug info Jiri Olsa
2018-01-11 6:24 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 03/12] perf: Allocate context task_ctx_data for child event Jiri Olsa
2018-01-08 12:14 ` Peter Zijlstra
2018-01-11 6:24 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 04/12] perf: Add sample_id to PERF_RECORD_ITRACE_START event comment Jiri Olsa
2018-01-11 6:25 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 05/12] perf: Make perf_callchain function static Jiri Olsa
2018-01-11 6:25 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 06/12] perf: Return empty callchain instead of NULL Jiri Olsa
2018-01-08 12:15 ` Peter Zijlstra [this message]
2018-01-11 6:26 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 07/12] perf: Update PERF_RECORD_MISC_* comment for perf_event_header::misc bit 13 Jiri Olsa
2018-01-11 6:26 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 08/12] perf script: Add support to display sample misc field Jiri Olsa
2018-01-11 6:27 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 09/12] perf script: Add support to display lost events Jiri Olsa
2018-01-10 15:40 ` Arnaldo Carvalho de Melo
2018-01-10 15:44 ` Jiri Olsa
2018-01-11 6:27 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 10/12] perf tools: Make the tool's warning messages optional Jiri Olsa
2018-01-11 6:27 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 11/12] perf report: Add --stat option to display quick data statistics Jiri Olsa
2018-01-11 6:28 ` [tip:perf/core] perf report: Add --stats " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 12/12] perf report: Add --task option to display monitored tasks Jiri Olsa
2018-01-08 15:55 ` Arnaldo Carvalho de Melo
2018-01-08 16:03 ` Arnaldo Carvalho de Melo
2018-01-09 1:56 ` Namhyung Kim
2018-01-09 9:15 ` Jiri Olsa
2018-01-09 13:05 ` Arnaldo Carvalho de Melo
2018-01-09 13:27 ` Jiri Olsa
2018-01-11 6:29 ` [tip:perf/core] perf report: Add --tasks " tip-bot for Jiri Olsa
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180108121516.GJ3040@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=acme@kernel.org \
--cc=ak@linux.intel.com \
--cc=alexander.shishkin@linux.intel.com \
--cc=dsahern@gmail.com \
--cc=jolsa@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=namhyung@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).