Hi,
Even if I set M_TRIM_THRESHOLD to 0, the lowest contiguous free block before the program break needs to be 64 KiB before it can be "trimmed". Is this a known fact, or am I doing something wrong here? I created a quick test program that calls malloc_stats (1) before any malloc operations, (2) after malloc of buflen bytes, and (3) after freeing the previously malloc-ed block. Here are some printouts.
acatovic@ubuntu:~/memdev$ ./malloc-prof
Usage: ./malloc-prof -b <N bytes> -n <NUM> [-t <X KiB>] [-p <Y KiB>]
-b <N bytes> Allocate a buffer of N bytes. Mandatory.
-n <NUM> Perform NUM number of malloc()/free() operations. Mandatory.
-t <X KiB> Set M_TRIM_THRESHOLD to X * 1024 bytes. See mallopt(3) for more info.
-p <Y KiB> Set M_TOP_PAD to Y * 1024 bytes. See mallopt(3) for more info.
acatovic@ubuntu:~/memdev$ ./malloc-prof -b 4096 -n 1 -p 0 -t 0
malloc_stats() BEFORE malloc():
Arena 0:
system bytes = 0
in use bytes = 0
Total (incl. mmap):
system bytes = 0
in use bytes = 0
max mmap regions = 0
max mmap bytes = 0
malloc_stats() AFTER malloc(), buflen=4096, num=1
Arena 0:
system bytes = 8192
in use bytes = 4104
Total (incl. mmap):
system bytes = 8192
in use bytes = 4104
max mmap regions = 0
max mmap bytes = 0
malloc_stats AFTER free():
Arena 0:
system bytes = 8192
in use bytes = 0
Total (incl. mmap):
system bytes = 8192
in use bytes = 0
max mmap regions = 0
max mmap bytes = 0
acatovic@ubuntu:~/memdev$ ./malloc-prof -b 32768 -n 1 -p 0 -t 0
malloc_stats() BEFORE malloc():
Arena 0:
system bytes = 0
in use bytes = 0
Total (incl. mmap):
system bytes = 0
in use bytes = 0
max mmap regions = 0
max mmap bytes = 0
malloc_stats() AFTER malloc(), buflen=32768, num=1
Arena 0:
system bytes = 36864
in use bytes = 32776
Total (incl. mmap):
system bytes = 36864
in use bytes = 32776
max mmap regions = 0
max mmap bytes = 0
malloc_stats AFTER free():
Arena 0:
system bytes = 36864
in use bytes = 0
Total (incl. mmap):
system bytes = 36864
in use bytes = 0
max mmap regions = 0
max mmap bytes = 0
acatovic@ubuntu:~/memdev$ ./malloc-prof -b 65536 -n 1 -p 0 -t 0
malloc_stats() BEFORE malloc():
Arena 0:
system bytes = 0
in use bytes = 0
Total (incl. mmap):
system bytes = 0
in use bytes = 0
max mmap regions = 0
max mmap bytes = 0
malloc_stats() AFTER malloc(), buflen=65536, num=1
Arena 0:
system bytes = 69632
in use bytes = 65544
Total (incl. mmap):
system bytes = 69632
in use bytes = 65544
max mmap regions = 0
max mmap bytes = 0
malloc_stats AFTER free():
Arena 0:
system bytes = 4096
in use bytes = 0
Total (incl. mmap):
system bytes = 4096
in use bytes = 0
max mmap regions = 0
max mmap bytes = 0
Not sure what info you need, but this is the libc version:
acatovic@ubuntu:~/memdev$ ldd malloc-prof
linux-gate.so.1 => (0xb7712000)
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb7555000)
/lib/ld-linux.so.2 (0xb7713000)
acatovic@ubuntu:~/memdev$ /lib/i386-linux-gnu/libc.so.6
GNU C Library (Ubuntu EGLIBC 2.15-0ubuntu10.5) stable release version 2.15, by Roland McGrath et al.
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.6.3.
Compiled on a Linux 3.2.50 system on 2013-09-30.
Available extensions:
crypt add-on version 2.1 by Michael Glad and others
GNU Libidn by Simon Josefsson
Native POSIX Threads Library by Ulrich Drepper et al
BIND-8.2.3-T5B
libc ABIs: UNIQUE IFUNC
For bug reporting instructions, please see:
<http://www.debian.org/Bugs/>.
Regards,
Armin Catovic
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
