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The soft maximum number of open files for a calling process is 1024, which is defined as INR_OPEN_CUR in include/uapi/linux/fs.h, and the hard maximum number of open files for a calling process is 4096, which is defined as INR_OPEN_MAX in include/uapi/linux/fs.h. Both INR_OPEN_CUR and INR_OPEN_MAX are used to limit the value of RLIMIT_NOFILE in include/asm-generic/resource.h. And the soft maximum number finally decides the limitation of the maximum files which are allowed to be opened. That is to say a process can use at most 1024 file descriptors for its o pened files, or an EMFILE error will happen. This error can be fixed by increasing the soft maximum number, under the constraint that the soft maximum number can not exceed the hard maximum number, or both soft and hard maximum number should be increased simultaneously with privilege. For perf sched replay, it uses sys_perf_event_open to create the file descriptor for each of the tasks in order to handle information of perf events. That is to say each task needs a unique file descriptor. In x86_64, there may be over 1024 or 4096 tasks correspoinding to the record in perf.data, which causes that no enough file descriptors can be used. As a result, EMFILE error happens and stops the replay process. To solve this problem, we adaptively increase the soft and hard maximum number of open files with a '-f' option. Example: Test environment: x86_64 with 160 cores $ cat /proc/sys/kernel/pid_max 163840 $ cat /proc/sys/fs/file-max 6815744 $ ulimit -Sn 1024 $ ulimit -Hn 4096 Before this patch: $ perf sched replay ... task 1549 ( :163132: 163132), nr_events: 1 task 1550 ( :163540: 163540), nr_events: 1 task 1551 ( <unknown>: 0), nr_events: 10 Error: sys_perf_event_open() syscall returned with -1 (Too many open files) After this patch: $ perf sched replay ... task 1549 ( :163132: 163132), nr_events: 1 task 1550 ( :163540: 163540), nr_events: 1 task 1551 ( <unknown>: 0), nr_events: 10 Error: sys_perf_event_open() syscall returned with -1 (Too many open files) Have a try with -f option $ perf sched replay -f ... task 1549 ( :163132: 163132), nr_events: 1 task 1550 ( :163540: 163540), nr_events: 1 task 1551 ( <unknown>: 0), nr_events: 10 ------------------------------------------------------------ #1 : 54.401, ravg: 54.40, cpu: 3285.21 / 3285.21 #2 : 199.548, ravg: 68.92, cpu: 4999.65 / 3456.66 #3 : 170.483, ravg: 79.07, cpu: 1349.94 / 3245.99 #4 : 192.034, ravg: 90.37, cpu: 1322.88 / 3053.67 #5 : 182.929, ravg: 99.62, cpu: 1406.51 / 2888.96 #6 : 152.974, ravg: 104.96, cpu: 1167.54 / 2716.82 #7 : 155.579, ravg: 110.02, cpu: 2992.53 / 2744.39 #8 : 130.557, ravg: 112.08, cpu: 1126.43 / 2582.59 #9 : 138.520, ravg: 114.72, cpu: 1253.22 / 2449.65 #10 : 134.328, ravg: 116.68, cpu: 1587.95 / 2363.48 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/1427809596-29559-8-git-send-email-yunlong.song@huawei.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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