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a35e27d0e5
Current MAX_PID is only 65536, which will cause assertion failure problem when CPU cores are more than 64 in x86_64. This is because the pid_max value in x86_64 is at least PIDS_PER_CPU_DEFAULT * num_possible_cpus() (see function pidmap_init defined in kernel/pid.c), where PIDS_PER_CPU_DEFAULT is 1024 (defined in include/linux/threads.h). Thus for MAX_PID = 65536, the correspoinding CPU cores are 65536/1024=64. This is obviously not enough at all for x86_64, and will cause an assertion failure problem due to BUG_ON(pid >= MAX_PID) in the codes. We increase MAX_PID value from 65536 to 1024*1000, which can be used in x86_64 with 1000 cores. This number is finally decided according to the limitation of stack size of calling process. Use 'ulimit -a', the result shows the stack size of any process is 8192 Kbytes, which is defined in include/uapi/linux/resource.h (#define _STK_LIM (8*1024*1024)). Thus we choose a large enough value for MAX_PID, and make it satisfy to the limitation of the stack size, i.e., making the perf process take up a memory space just smaller than 8192 Kbytes. We have calculated and tested that 1024*1000 is OK for MAX_PID. This means perf sched replay can now be used with at most 1000 cores in x86_64 without any assertion failure problem. Example: Test environment: x86_64 with 160 cores $ cat /proc/sys/kernel/pid_max 163840 Before this patch: $ perf sched replay run measurement overhead: 240 nsecs sleep measurement overhead: 55379 nsecs the run test took 1000004 nsecs the sleep test took 1059424 nsecs perf: builtin-sched.c:330: register_pid: Assertion `!(pid >= 65536)' failed. Aborted After this patch: $ perf sched replay run measurement overhead: 221 nsecs sleep measurement overhead: 55397 nsecs the run test took 999920 nsecs the sleep test took 1053313 nsecs nr_run_events: 10 nr_sleep_events: 1562 nr_wakeup_events: 5 task 0 ( :1: 1), nr_events: 1 task 1 ( :2: 2), nr_events: 1 task 2 ( :3: 3), nr_events: 1 task 3 ( :5: 5), nr_events: 1 ... Signed-off-by: Yunlong Song <yunlong.song@huawei.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Wang Nan <wangnan0@huawei.com> Link: http://lkml.kernel.org/r/1427809596-29559-3-git-send-email-yunlong.song@huawei.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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| .. | ||
| arch | ||
| bench | ||
| config | ||
| Documentation | ||
| python | ||
| scripts | ||
| tests | ||
| ui | ||
| util | ||
| .gitignore | ||
| Build | ||
| builtin-annotate.c | ||
| builtin-bench.c | ||
| builtin-buildid-cache.c | ||
| builtin-buildid-list.c | ||
| builtin-data.c | ||
| builtin-diff.c | ||
| builtin-evlist.c | ||
| builtin-help.c | ||
| builtin-inject.c | ||
| builtin-kmem.c | ||
| builtin-kvm.c | ||
| builtin-list.c | ||
| builtin-lock.c | ||
| builtin-mem.c | ||
| builtin-probe.c | ||
| builtin-record.c | ||
| builtin-report.c | ||
| builtin-sched.c | ||
| builtin-script.c | ||
| builtin-stat.c | ||
| builtin-timechart.c | ||
| builtin-top.c | ||
| builtin-trace.c | ||
| builtin.h | ||
| command-list.txt | ||
| CREDITS | ||
| design.txt | ||
| Makefile | ||
| Makefile.perf | ||
| MANIFEST | ||
| perf-archive.sh | ||
| perf-completion.sh | ||
| perf-read-vdso.c | ||
| perf-sys.h | ||
| perf-with-kcore.sh | ||
| perf.c | ||
| perf.h | ||