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Message-ID: <33dd0a17-cf35-4b6b-9ee5-9983669cc98b@huawei.com>
Date: Fri, 9 May 2025 09:54:19 +0800
From: Zenghui Yu <yuzenghui@...wei.com>
To: Haixin Yu <yuhaixin.yhx@...ux.alibaba.com>
CC: John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>, James
Clark <james.clark@....com>, Mike Leach <mike.leach@...aro.org>, Leo Yan
<leo.yan@...aro.org>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar
<mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland
<mark.rutland@....com>, Alexander Shishkin
<alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Namhyung
Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>, Adrian Hunter
<adrian.hunter@...el.com>, "Liang, Kan" <kan.liang@...ux.intel.com>,
<linux-arm-kernel@...ts.infradead.org>, <linux-perf-users@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, Shannon Zhao
<shannon.zhao@...ux.alibaba.com>, Sergey Senozhatsky
<sergey.senozhatsky@...il.com>
Subject: Re: [PATCH] perf kvm: Fix arm64 VM-EXIT event detection
[ +Cc the original author of perf kvm stat ]
On 2023/8/8 11:57, Haixin Yu wrote:
> A VM-EXIT event shall start at kvm:kvm_exit, and end with the next
> kvm:kvm_entry. But it's reversed on arm64, which means the time running
> guest code in fact.
Good catch! It'd be great if Sergey could take a look.
>
> Example:
>
> # perf kvm stat record -p 2772 -- sleep 1
>
> Before this change:
>
> # perf kvm stat report
>
> Analyze events for all VMs, all VCPUs:
>
> VM-EXIT Samples Samples% Time% Min Time Max Time Avg time
>
> IRQ 756 100.00% 100.00% 2.28us 3674.38us 1375.66us ( +- 4.34% )
>
> Total Samples:756, Total events handled time:1039996.94us.
>
> After:
>
> # perf kvm stat report
>
> Analyze events for all VMs, all VCPUs:
>
> VM-EXIT Samples Samples% Time% Min Time Max Time Avg time
>
> IRQ 772 100.00% 100.00% 0.24us 62.86us 6.34us ( +- 3.55% )
>
> Total Samples:772, Total events handled time:4890.80us.
>
> IRQ average handled time decreases to 6us, which is a more rational result
> as KVM handles IRQ by returning to guest directly.
>
> Signed-off-by: Haixin Yu <yuhaixin.yhx@...ux.alibaba.com>
> ---
> tools/perf/arch/arm64/util/kvm-stat.c | 24 +++---------------------
> tools/perf/builtin-kvm.c | 2 +-
> 2 files changed, 4 insertions(+), 22 deletions(-)
>
> diff --git a/tools/perf/arch/arm64/util/kvm-stat.c b/tools/perf/arch/arm64/util/kvm-stat.c
> index 6611aa21cba9..eeb659ceedc2 100644
> --- a/tools/perf/arch/arm64/util/kvm-stat.c
> +++ b/tools/perf/arch/arm64/util/kvm-stat.c
> @@ -21,7 +21,7 @@ const char *kvm_events_tp[] = {
> NULL,
> };
>
> -static void event_get_key(struct evsel *evsel,
> +void exit_event_get_key(struct evsel *evsel,
> struct perf_sample *sample,
> struct event_key *key)
> {
> @@ -40,27 +40,9 @@ static void event_get_key(struct evsel *evsel,
> }
> }
>
> -static bool event_begin(struct evsel *evsel,
> - struct perf_sample *sample __maybe_unused,
> - struct event_key *key __maybe_unused)
> -{
> - return evsel__name_is(evsel, kvm_entry_trace);
> -}
> -
> -static bool event_end(struct evsel *evsel,
> - struct perf_sample *sample,
> - struct event_key *key)
> -{
> - if (evsel__name_is(evsel, kvm_exit_trace)) {
> - event_get_key(evsel, sample, key);
> - return true;
> - }
> - return false;
> -}
> -
> static struct kvm_events_ops exit_events = {
> - .is_begin_event = event_begin,
> - .is_end_event = event_end,
> + .is_begin_event = exit_event_begin,
> + .is_end_event = exit_event_end,
> .decode_key = exit_event_decode_key,
> .name = "VM-EXIT"
> };
> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> index 71165036e4ca..498cd8e21134 100644
> --- a/tools/perf/builtin-kvm.c
> +++ b/tools/perf/builtin-kvm.c
> @@ -615,7 +615,7 @@ static const char *get_filename_for_perf_kvm(void)
>
> #if defined(HAVE_KVM_STAT_SUPPORT) && defined(HAVE_LIBTRACEEVENT)
>
> -void exit_event_get_key(struct evsel *evsel,
> +void __weak exit_event_get_key(struct evsel *evsel,
> struct perf_sample *sample,
> struct event_key *key)
> {
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