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Date: Fri, 17 May 2013 10:16:40 +0800
From: Ming Lei <ming.lei@...onical.com>
To: Tejun Heo <tj@...nel.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Will Deacon <will.deacon@....com>,
Russell King - ARM Linux <linux@....linux.org.uk>,
Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: [Bug] ARM 'perf' regression by commit a43cb95d5
Hi,
The commit a43cb95d5(dump_stack: unify debug information printed by show_regs())
caused ARM perf regression, then 'perf top' outputs mistakenly, see
[1]. The correct
output should be [2], which can be got after reverting the commit or
doing it partly
by the one line change below:
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index f219703..89bc3a4 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -225,7 +225,7 @@ void __show_regs(struct pt_regs *regs)
unsigned long flags;
char buf[64];
- show_regs_print_info(KERN_DEFAULT);
+ //show_regs_print_info(KERN_DEFAULT);
Looks a bit weird, anyone can give a hint?
Thanks,
--
Ming Lei
[1], 'perf top' mistaken output
Samples: 17K of event 'cpu-clock', Event count (approx.): 3516532661
97.51% [smsc95xx] [k] 0x013645b8
0.21% libc-2.15.so [.] strstr
0.14% libc-2.15.so [.] strchr
0.12% libc-2.15.so [.] strcmp
0.12% perf [.] perf_evsel__parse_sample
0.09% perf [.] symbols__insert
0.09% perf [.] dso__load_sym
0.08% perf [.] perf_top__mmap_read_idx
0.08% perf [.] symbol_filter
0.07% libc-2.15.so [.] memchr
0.07% libc-2.15.so [.] memset
0.07% perf [.] internal_cplus_demangle
0.06% perf [.] sort__dso_cmp
0.06% libc-2.15.so [.] strncmp
0.06% perf [.] add_hist_entry.isra.2
0.06% perf [.] dso__find_symbol
0.06% libc-2.15.so [.] _int_malloc
0.05% perf [.] 0x00010d60
0.04% libc-2.15.so [.] memcpy
0.04% perf [.] map__find_symbol
0.04% perf [.] rb_next
0.04% libelf-0.154.so [.] gelf_getsym
[2], 'perf top' correct output
Samples: 46K of event 'cpu-clock', Event count (approx.): 937128704
96.44% [kernel] [k] cpuidle_enter_state
0.19% libc-2.15.so [.] strstr
0.16% [kernel] [k] kallsyms_expand_symbol.clone.0
0.13% [kernel] [k] _raw_spin_unlock_irq
0.13% [kernel] [k] _raw_spin_unlock_irqrestore
0.10% [kernel] [k] format_decode
0.10% perf [.] perf_top__mmap_read_idx
0.10% perf [.] rb_next
0.09% perf [.] dso__find_symbol
0.08% [kernel] [k] vsnprintf
0.08% perf [.] add_hist_entry.isra.2
0.08% libc-2.15.so [.] strcmp
0.08% libc-2.15.so [.] memchr
0.07% perf [.] sort__dso_cmp
0.07% libc-2.15.so [.] strchr
0.07% [kernel] [k] number.clone.1
0.07% perf [.] map__process_kallsym_symbol
0.06% [kernel] [k] memcpy
0.05% perf [.] perf_evsel__parse_sample
0.05% libc-2.15.so [.] _int_malloc
0.05% libc-2.15.so [.] memcpy
0.05% perf [.] perf_event__preprocess_sample
--
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