Re: [PATCH] perf tools: allow overriding MAX_NR_CPUS at compile time
From: Arnaldo Carvalho de Melo <acme@kernel.org>
Date: 2017-09-22 14:09:35
Also in:
lkml
Em Fri, Sep 22, 2017 at 01:20:43PM +0200, Christophe Leroy escreveu:
quoted hunk ↗ jump to hunk
After update of kernel, 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
I'll probably apply this, but the right thing would be to get rid of
MAX_NR_CPUS completely and instead allocate that using sysconf:
[root@jouet ~]# perf trace -e open,getdents getconf _NPROCESSORS_CONF
4
0.014 ( 0.011 ms): getconf/2452 open(filename: /etc/ld.so.cache, flags: CLOEXEC ) = 3
0.045 ( 0.008 ms): getconf/2452 open(filename: /lib64/libc.so.6, flags: CLOEXEC ) = 3
0.264 ( 0.012 ms): getconf/2452 open(filename: /usr/lib/locale/locale-archive, flags: CLOEXEC ) = 3
0.315 ( 0.028 ms): getconf/2452 open(filename: /sys/devices/system/cpu, flags: CLOEXEC|DIRECTORY|NONBLOCK) = 3
0.349 ( 0.013 ms): getconf/2452 getdents(fd: 3</sys/devices/system/cpu>, dirent: 0x944030, count: 32768) = 624
0.365 ( 0.001 ms): getconf/2452 getdents(fd: 3</sys/devices/system/cpu>, dirent: 0x944030, count: 32768) = 0
[root@jouet ~]#
quoted hunk ↗ jump to hunk
Signed-off-by: Christophe Leroy <redacted> --- tools/perf/perf.h | 2 ++ 1 file changed, 2 insertions(+)diff --git a/tools/perf/perf.h b/tools/perf/perf.h index dc442ba21bf6..a9db563da0a9 100644 --- a/tools/perf/perf.h +++ b/tools/perf/perf.h@@ -23,7 +23,9 @@ static inline unsigned long long rdclock(void) 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;-- 2.13.3