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Originally, (refer commitf90d194a86("perf evlist: Do not poll events that use the system_wide flag") there wasn't much reason to poll system-wide events because: 1. The mmaps get "merged" via set-output anyway (the per-cpu case) 2. perf reads all mmaps when any event is woken 3. system-wide mmaps do not fill up as fast as the mmaps for user selected events But there was 1 reason not to poll which was that it prevented correct termination due to POLLHUP on all user selected events. That issue is now easily resolved by using fdarray_flag__nonfilterable. With the advent of commitae4f8ae16a("libperf evlist: Allow mixing per-thread and per-cpu mmaps"), system-wide mmaps can be used also in the per-thread case where reason 1 does not apply. Fix the omission of system-wide events from polling by using the fdarray_flag__nonfilterable flag. Example: Before: $ perf record --no-bpf-event -vvv -e intel_pt// --per-thread uname 2>err.txt Linux $ grep 'sys_perf_event_open.*=\|pollfd' err.txt sys_perf_event_open: pid 155076 cpu -1 group_fd -1 flags 0x8 = 5 sys_perf_event_open: pid 155076 cpu -1 group_fd -1 flags 0x8 = 6 sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 7 sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 9 sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8 = 10 sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8 = 11 sys_perf_event_open: pid -1 cpu 4 group_fd -1 flags 0x8 = 12 sys_perf_event_open: pid -1 cpu 5 group_fd -1 flags 0x8 = 13 sys_perf_event_open: pid -1 cpu 6 group_fd -1 flags 0x8 = 14 sys_perf_event_open: pid -1 cpu 7 group_fd -1 flags 0x8 = 15 thread_data[0x55fb43c29e80]: pollfd[0] <- event_fd=5 thread_data[0x55fb43c29e80]: pollfd[1] <- event_fd=6 thread_data[0x55fb43c29e80]: pollfd[2] <- non_perf_event fd=4 After: $ perf record --no-bpf-event -vvv -e intel_pt// --per-thread uname 2>err.txt Linux $ grep 'sys_perf_event_open.*=\|pollfd' err.txt sys_perf_event_open: pid 156316 cpu -1 group_fd -1 flags 0x8 = 5 sys_perf_event_open: pid 156316 cpu -1 group_fd -1 flags 0x8 = 6 sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 7 sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 9 sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8 = 10 sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8 = 11 sys_perf_event_open: pid -1 cpu 4 group_fd -1 flags 0x8 = 12 sys_perf_event_open: pid -1 cpu 5 group_fd -1 flags 0x8 = 13 sys_perf_event_open: pid -1 cpu 6 group_fd -1 flags 0x8 = 14 sys_perf_event_open: pid -1 cpu 7 group_fd -1 flags 0x8 = 15 thread_data[0x55cc19e58e80]: pollfd[0] <- event_fd=5 thread_data[0x55cc19e58e80]: pollfd[1] <- event_fd=6 thread_data[0x55cc19e58e80]: pollfd[2] <- event_fd=7 thread_data[0x55cc19e58e80]: pollfd[3] <- event_fd=9 thread_data[0x55cc19e58e80]: pollfd[4] <- event_fd=10 thread_data[0x55cc19e58e80]: pollfd[5] <- event_fd=11 thread_data[0x55cc19e58e80]: pollfd[6] <- event_fd=12 thread_data[0x55cc19e58e80]: pollfd[7] <- event_fd=13 thread_data[0x55cc19e58e80]: pollfd[8] <- event_fd=14 thread_data[0x55cc19e58e80]: pollfd[9] <- event_fd=15 thread_data[0x55cc19e58e80]: pollfd[10] <- non_perf_event fd=4 Fixes:ae4f8ae16a("libperf evlist: Allow mixing per-thread and per-cpu mmaps") Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Cc: Ian Rogers <irogers@google.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220915122612.81738-3-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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.