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From: "jtaylor.debian at googlemail dot com" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug malloc/17195] New: excessive heap trimming in threaded programs Date: Thu, 24 Jul 2014 11:04:00 -0000 [thread overview] Message-ID: <bug-17195-131@http.sourceware.org/bugzilla/> (raw) https://sourceware.org/bugzilla/show_bug.cgi?id=17195 Bug ID: 17195 Summary: excessive heap trimming in threaded programs Product: glibc Version: 2.19 Status: NEW Severity: normal Priority: P2 Component: malloc Assignee: unassigned at sourceware dot org Reporter: jtaylor.debian at googlemail dot com using glibc 2.19 from ubuntu 14.04 amd64 the following simple program causes a huge amount of page faults due to the heap being trimmed on every second free() even though heap trimming was disabled and the mmap threshold is set to the maximum: #include <stdlib.h> #include <string.h> #include <stdio.h> #include <malloc.h> int main(int argc, const char *argv[]) { mallopt (M_TRIM_THRESHOLD, -1); mallopt (M_MMAP_THRESHOLD, 1024*1024*32); #pragma omp parallel for num_threads(2) for (size_t i = 0; i < 1000; i++) { size_t n = 1024*1024*16; double * m = malloc(n); memset(m, 1, n); free(m); } return 0; } gcc test.c -std=c99 -g -O2 -fopenmp perf stat -e page-faults ./a.out 2,036,312 page-faults strace -f -e madvise ./a.out 2>&1 | grep MADV_DONTNEED | wc -l 500 when setting the number of threads to 1 it reuses the memory as expected: perf stat -e page-faults ./a.out 4,271 page-faults -- You are receiving this mail because: You are on the CC list for the bug.
next reply other threads:[~2014-07-24 11:04 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-07-24 11:04 jtaylor.debian at googlemail dot com [this message] 2014-07-24 11:07 ` [Bug malloc/17195] excessive heap trimming in threaded programs even when disabled with mallopt jtaylor.debian at googlemail dot com 2014-08-30 12:34 ` neleai at seznam dot cz 2014-08-30 12:40 ` jtaylor.debian at googlemail dot com 2015-02-12 17:46 ` jtaylor.debian at googlemail dot com 2015-02-18 5:48 ` siddhesh at redhat dot com 2015-04-02 6:46 ` cvs-commit at gcc dot gnu.org 2015-04-02 6:48 ` siddhesh at redhat dot com 2015-10-08 2:23 ` cvs-commit at gcc dot gnu.org
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