Messages in this thread Patch in this message | | | Date | Fri, 04 Jan 2008 13:51:31 +0200 | From | Török Edwin <> | Subject | Re: Improve hackbench |
| |
Ingo Molnar wrote: > * Zhang, Yanmin <yanmin_zhang@linux.intel.com> wrote: > > >> hackbench is to test Linux scheduler. The original program is at >> http://devresources.linux-foundation.org/craiger/hackbench/src/hackbench.c >> Based on this multi-process version, a nice person created a >> multi-thread version. Pls. see >> http://www.bullopensource.org/posix/pi-futex/hackbench_pth.c >> > > great. I've uploaded your unified & improved version to: > > http://redhat.com/~mingo/cfs-scheduler/tools/hackbench.c > > (i made some small changes - two warning fixes on gcc 4.2 and a default > of 10 groups when hackbench is called without parameters, plus a > printout.) >
On x86-64 there's a bug [*], that causes hackbench to segfault when compiled with optimizations: in reap_worker(): int status; ... pthread_join(id, (void **)(void *)&status);
That is not correct, sizeof(void*) > sizeof(int) on x86-64. Something gets overwritten on the stack, I tried with gcc -fstack-protector, but it doesn't detect it !? After applying the patch, it no longer segfaults.
This patch fixes it: --- hackbench.c 2008-01-04 10:08:26.000000000 +0200 +++ ../hackbench.c 2008-01-04 13:45:22.000000000 +0200 @@ -241,8 +241,10 @@ wait(&status); if (!WIFEXITED(status)) exit(1); - } else - pthread_join(id, (void **)(void *)&status); + } else { + void* status; + pthread_join(id, (void **)&status); + } }
/* One group of senders and receivers */ ----------------
I also notice that the thread version is slower, than process version:
$ ./hackbench 5 thread Running with 5*40 (== 200) tasks. Time: 0.413 $ ./hackbench 5 thread Running with 5*40 (== 200) tasks. Time: 0.423 $ ./hackbench 5 thread 20 Running with 5*40 (== 200) tasks. Time: 0.093 $ ./hackbench 5 thread 200 Running with 5*40 (== 200) tasks. Time: 0.827 $ ./hackbench 5 thread 2000 Running with 5*40 (== 200) tasks. Time: 8.409 $ ./hackbench 5 process 2000 Running with 5*40 (== 200) tasks. Time: 7.669 $ ./hackbench -pipe 5 process 2000 Running with 5*40 (== 200) tasks. Time: 3.416 $ ./hackbench -pipe 5 thread 2000 Running with 5*40 (== 200) tasks. Time: 4.320
[*] $ uname -a Linux lightspeed2 2.6.24-rc6-ge697789d #3 Wed Jan 2 11:15:05 EET 2008 x86_64 GNU/Linux $ gcc -v Using built-in specs. Target: x86_64-linux-gnu Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2 --enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 4.2.3 20071123 (prerelease) (Debian 4.2.2-4) $ wget http://redhat.com/~mingo/cfs-scheduler/tools/hackbench.c --13:40:53-- http://redhat.com/~mingo/cfs-scheduler/tools/hackbench.c => `hackbench.c' Resolving redhat.com... 209.132.177.50 Connecting to redhat.com|209.132.177.50|:80... connected. HTTP request sent, awaiting response... 302 Found Location: http://www.redhat.com/~mingo/cfs-scheduler/tools/hackbench.c [following] --13:40:54-- http://www.redhat.com/~mingo/cfs-scheduler/tools/hackbench.c => `hackbench.c' Resolving www.redhat.com... 209.132.177.50 Connecting to www.redhat.com|209.132.177.50|:80... connected. HTTP request sent, awaiting response... 301 Moved Permanently Location: http://people.redhat.com/mingo/cfs-scheduler/tools/hackbench.c [following] --13:40:54-- http://people.redhat.com/mingo/cfs-scheduler/tools/hackbench.c => `hackbench.c' Resolving people.redhat.com... 66.187.233.237 Connecting to people.redhat.com|66.187.233.237|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 8,455 (8.3K) [text/plain] 100%[====================================================================================================================>] 8,455 --.--K/s 13:40:55 (61.93 KB/s) - `hackbench.c' saved [8455/8455]
$ gcc -O2 -g -Wall -o hackbench hackbench.c -lpthread hackbench.c:32:66: warning: missing terminating ' character $ ./hackbench 1 thread Running with 1*40 (== 40) tasks. Segmentation fault
$ valgrind --trace-children=yes ./hackbench 1 thread ==27332== Memcheck, a memory error detector. ==27332== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al. ==27332== Using LibVEX rev 1804, a library for dynamic binary translation. ==27332== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP. ==27332== Using valgrind-3.3.0-Debian, a dynamic binary instrumentation framework. ==27332== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al. ==27332== For more details, rerun with: -v ==27332== Running with 1*40 (== 40) tasks. ==27332== Thread 2: ==27332== Syscall param write(buf) points to uninitialised byte(s) ==27332== at 0x4C1854B: (within /usr/lib/debug/libpthread-2.7.so) ==27332== by 0x400C34: ready (hackbench.c:138) ==27332== by 0x400C97: receiver (hackbench.c:182) ==27332== by 0x4C113F6: start_thread (pthread_create.c:297) ==27332== by 0x4EFD91C: clone (in /usr/lib/debug/libc-2.7.so) ==27332== Address 0x558a09f is on thread 2's stack ==27332== ==27332== Thread 22: ==27332== Syscall param write(buf) points to uninitialised byte(s) ==27332== at 0x4C1854B: (within /usr/lib/debug/libpthread-2.7.so) ==27332== by 0x400C34: ready (hackbench.c:138) ==27332== by 0x400D33: sender (hackbench.c:152) ==27332== by 0x4C113F6: start_thread (pthread_create.c:297) ==27332== by 0x4EFD91C: clone (in /usr/lib/debug/libc-2.7.so) ==27332== Address 0x55da07f is on thread 22's stack ==27332== ==27332== Thread 40: ==27332== Syscall param write(buf) points to uninitialised byte(s) ==27332== at 0x4C1854B: (within /usr/lib/debug/libpthread-2.7.so) ==27332== by 0x400D6E: sender (hackbench.c:160) ==27332== by 0x4C113F6: start_thread (pthread_create.c:297) ==27332== by 0x4EFD91C: clone (in /usr/lib/debug/libc-2.7.so) ==27332== Address 0x56220a0 is on thread 40's stack ==27332== ==27332== Thread 1: ==27332== Jump to the invalid address stated on the next line ==27332== at 0x0: ??? ==27332== by 0x518702F: ??? ==27332== by 0xFFFFFFFF: ??? ==27332== by 0x518702F: ??? ==27332== by 0x2800000000: ??? ==27332== Address 0x0 is not stack'd, malloc'd or (recently) free'd ==27332== ==27332== Process terminating with default action of signal 11 (SIGSEGV) ==27332== Bad permissions for mapped region at address 0x0 ==27332== at 0x0: ??? ==27332== by 0x518702F: ??? ==27332== by 0xFFFFFFFF: ??? ==27332== by 0x518702F: ??? ==27332== by 0x2800000000: ??? ==27332== ==27332== ERROR SUMMARY: 40041 errors from 4 contexts (suppressed: 8 from 1) ==27332== malloc/free: in use at exit: 11,420 bytes in 61 blocks. ==27332== malloc/free: 62 allocs, 1 frees, 11,692 bytes allocated. ==27332== For counts of detected errors, rerun with: -v ==27332== searching for pointers to 61 not-freed blocks. ==27332== checked 560,688 bytes. ==27332== ==27332== LEAK SUMMARY: ==27332== definitely lost: 20 bytes in 1 blocks. ==27332== possibly lost: 10,608 bytes in 39 blocks. ==27332== still reachable: 792 bytes in 21 blocks. ==27332== suppressed: 0 bytes in 0 blocks. ==27332== Rerun with --leak-check=full to see details of leaked memory. Segmentation fault
Best regards, --Edwin
| |