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![]() Threads share map_groups, all map events are merged into it. Thus we could send mmaps only for thread group leader. Otherwise it took ages to attach and record something from processes with many vmas and threads. Thread group leader could be already dead, but it seems perf cannot handle this case anyway. Testing dummy: #include <stdio.h> #include <stdlib.h> #include <sys/mman.h> #include <pthread.h> #include <unistd.h> void *thread(void *arg) { pause(); } int main(int argc, char **argv) { int threads = 10000; int vmas = 50000; pthread_t th; for (int i = 0; i < threads; i++) pthread_create(&th, NULL, thread, NULL); for (int i = 0; i < vmas; i++) mmap(NULL, 4096, (i & 1) ? PROT_READ : PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0); sleep(60); return 0; } Comment by Jiri Olsa: We actualy synthesize the group leader (if we found one) for the thread even if it's not present in the thread_map, so the process maps are always in data. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Acked-by: Jiri Olsa <jolsa@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/153363294102.396323.6277944760215058174.stgit@buzz Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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README |
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. See Documentation/00-INDEX for a list of what is contained in each file. 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.