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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) 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> Acked-by: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20231013075945.698874-1-yangjihong1@huawei.com Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.