Messages in this thread | | | Subject | Re: [PATCH] perf data: Increase RLIMIT_NOFILE limit when open too many files in perf_data__create_dir() | From | Yang Jihong <> | Date | Sat, 21 Oct 2023 09:47:33 +0800 |
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Hello,
On 2023/10/20 13:59, Namhyung Kim wrote: > Hello, > > On Fri, Oct 13, 2023 at 1:01 AM Yang Jihong <yangjihong1@huawei.com> wrote: >> >> If using parallel threads to collect data, perf record needs at least 6 fds >> per CPU. (one for sys_perf_event_open, four for pipe msg and ack of the >> pipe, see record__thread_data_open_pipes(), and one for open perf.data.XXX) > > Yep, probably one more for the dummy event. > >> For an environment with more than 100 cores, if perf record uses both >> `-a` and `--threads` options, it is easy to exceed the upper limit of the >> file descriptor number, when we run out of them try to increase the limits. >> >> Before: >> $ ulimit -n >> 1024 >> $ lscpu | grep 'On-line CPU(s)' >> On-line CPU(s) list: 0-159 >> $ perf record --threads -a sleep 1 >> Failed to create data directory: Too many open files >> >> After: >> $ ulimit -n >> 1024 >> $ lscpu | grep 'On-line CPU(s)' >> On-line CPU(s) list: 0-159 >> $ perf record --threads -a sleep 1 >> [ perf record: Woken up 1 times to write data ] >> [ perf record: Captured and wrote 0.394 MB perf.data (1576 samples) ] >> Signed-off-by: Yang Jihong <yangjihong1@huawei.com> >> --- >> tools/perf/util/data.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c >> index fc16299c915f..098f9e3bb2e7 100644 >> --- a/tools/perf/util/data.c >> +++ b/tools/perf/util/data.c >> @@ -17,6 +17,7 @@ >> #include "util.h" // rm_rf_perf_data() >> #include "debug.h" >> #include "header.h" >> +#include "evsel.h" >> #include <internal/lib.h> >> >> static void close_dir(struct perf_data_file *files, int nr) >> @@ -35,6 +36,7 @@ void perf_data__close_dir(struct perf_data *data) >> >> int perf_data__create_dir(struct perf_data *data, int nr) >> { >> + enum rlimit_action set_rlimit = NO_CHANGE; >> struct perf_data_file *files = NULL; >> int i, ret; >> >> @@ -54,11 +56,21 @@ int perf_data__create_dir(struct perf_data *data, int nr) >> goto out_err; >> } >> >> +retry_open: >> ret = open(file->path, O_RDWR|O_CREAT|O_TRUNC, S_IRUSR|S_IWUSR); >> if (ret < 0) { >> + /* >> + * If using parallel threads to collect data, >> + * perf record needs at least 6 fds per CPU. >> + * When we run out of them try to increase the limits. >> + */ >> + if (errno == EMFILE && evsel__increase_rlimit(&set_rlimit)) > > It seems weird that we have this helper with evsel prefix and > it does nothing with evsel. But it's a separate concern, so > > Acked-by: Namhyung Kim <namhyung@kernel.org> Thanks for the Acked-by tag.
Uh... The name of this helper doesn't seem to be appropriate. Okay, I'll submit a patch to fix this helper name.
Thanks, Yang
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