[PATCH 4.9 31/70] perf tools: Allow overriding MAX_NR_CPUS at compile time

Greg Kroah-Hartman
2018-09-17T22:54:55Z

From: Christophe Leroy <christophe.leroy@c-s.fr>

[ Upstream commit 21b8732eb4479b579bda9ee38e62b2c312c2a0e5 ]

After update of kernel, the perf tool doesn't run anymore on my 32MB RAM
powerpc board, but still runs on a 128MB RAM board:

~# strace perf
execve("/usr/sbin/perf", ["perf"], [/* 12 vars */]) = -1 ENOMEM (Cannot allocate memory)
--- SIGSEGV {si_signo=SIGSEGV, si_code=SI_KERNEL, si_addr=0} ---
+++ killed by SIGSEGV +++
Segmentation fault

objdump -x shows that .bss section has a huge size of 24Mbytes:

27 .bss 016baca8 101cebb8 101cebb8 001cd988 2**3

With especially the following objects having quite big size:

10205f80 l O .bss 00140000 runtime_cycles_stats
10345f80 l O .bss 00140000 runtime_stalled_cycles_front_stats
10485f80 l O .bss 00140000 runtime_stalled_cycles_back_stats
105c5f80 l O .bss 00140000 runtime_branches_stats
10705f80 l O .bss 00140000 runtime_cacherefs_stats
10845f80 l O .bss 00140000 runtime_l1_dcache_stats
10985f80 l O .bss 00140000 runtime_l1_icache_stats
10ac5f80 l O .bss 00140000 runtime_ll_cache_stats
10c05f80 l O .bss 00140000 runtime_itlb_cache_stats
10d45f80 l O .bss 00140000 runtime_dtlb_cache_stats
10e85f80 l O .bss 00140000 runtime_cycles_in_tx_stats
10fc5f80 l O .bss 00140000 runtime_transaction_stats
11105f80 l O .bss 00140000 runtime_elision_stats
11245f80 l O .bss 00140000 runtime_topdown_total_slots
11385f80 l O .bss 00140000 runtime_topdown_slots_retired
114c5f80 l O .bss 00140000 runtime_topdown_slots_issued
11605f80 l O .bss 00140000 runtime_topdown_fetch_bubbles
11745f80 l O .bss 00140000 runtime_topdown_recovery_bubbles

This is due to commit 4d255766d28b1 ("perf: Bump max number of cpus
to 1024"), because many tables are sized with MAX_NR_CPUS

This patch gives the opportunity to redefine MAX_NR_CPUS via

$ make EXTRA_CFLAGS=-DMAX_NR_CPUS=1

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20170922112043.8349468C57@po15668-vm-win7.idsi0.si.c-s.fr
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/perf/perf.h | 2 ++
1 file changed, 2 insertions(+)

--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -22,7 +22,9 @@ static inline unsigned long long rdclock
return ts.tv_sec * 1000000000ULL + ts.tv_nsec;
}

+#ifndef MAX_NR_CPUS
#define MAX_NR_CPUS 1024
+#endif

extern const char *input_name;
extern bool perf_host, perf_guest;