Messages in this thread | | | From | "Etienne Lorrain" <> | Date | Fri, 7 Aug 1998 11:47:07 +0001 | Subject | Re: gcc 2.7.1 |
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On Wed, 5 Aug 1998, Linus Torvalds wrote: > On Wed, 5 Aug 1998, Etienne Lorrain wrote: > > Maybe it is time to upgrade to gcc-2.7.3, so that this patch could > > be applied in the main stream : > > Do you have numbers for the effect of "-fno-strength-reduce"? Back when I > added it I couldn't see any difference at all to any benchmarks, so I've > had no real incentive to even try to remove it. > > Does anybody have any numbers that show that it actually matters for the > kernel (I know it matters a lot for some other things, but I'm looking for > something that really makes a difference in kernel-land)?
Hi,
I have done some benchmarking of the kernel (and not benchmarking of gcc), and you are _again_ right...
Here is what I've done:
---------------------------- Measures concerning no-strength-reduce optimisation:
Basic script to test filesystem,processor,I/O - just after reboot, nothing else running (shell /bin/bash) with linux-2.1.105-pre4 as kernel (cut and paste it with mouse/gpm), no X-window : *** save your data before: directory /usr/src/linux **** *** and file linux1.tar.gz ARE ERASED ****
cd /usr/src rm -rf linux1.tar.gz linux result cp linux-2.0.30.tar.gz linux1.tar.gz # not too big for my 386!
# REBOOT HERE
date > result ; \ cat /proc/version >> result ; \ cat /proc/meminfo >> result ; \ cat /proc/cpuinfo | grep bogomips >> result ; \ echo "gunzip linux1.tar.gz" >> result ; \ time --append -o result gunzip linux1.tar.gz ; \ echo "tar -xf linux1.tar" >> result ; \ time --append -o result tar -xf linux1.tar ; \ echo "rm -f linux1.tar" >> result ; \ time --append -o result rm -f linux1.tar ; \ echo "tar -czf linux1.tar.gz linux" >> result ; \ time --append -o result tar -czf linux1.tar.gz linux ; \ echo "parallel find :" >> result ; \ date >> result ; \ find linux -name "*.c" -exec grep "code" \{\} \; & \ find linux -name "*.h" -exec grep "define" \{\} \; & \ find linux -name "*.[ch]" -exec cat \{\} \; | wc & \ wait ; \ date >> result ; \ echo "rm -rf linux" >> result ; \ time --append -o result rm -rf linux ; \ date >> result
---------------------------- Without option -fno-strength-reduce (edited to fit):
Thu Aug 6 21:20:38 CEST 1998 Linux version 2.1.115 (root@xxxxxx.sony.de) (gcc version 2.7.2.3) #1 Thu Aug 6 14:49:34 CEST 1998 total: used: free: shared: buffers: cached: Mem: 15155200 7475200 7680000 7811072 757760 3055616 Swap: 50511872 0 50511872 MemTotal: 14800 kB MemFree: 7500 kB MemShared: 7628 kB Buffers: 740 kB Cached: 2984 kB SwapTotal: 49328 kB SwapFree: 49328 kB bogomips : 6.27
gunzip linux1.tar.gz 88.39user 20.37system 2:02.31elapsed 88%CPU (1604major+33minor)pagefaults 0swaps
tar -xf linux1.tar 21.15user 47.46system 1:33.48elapsed 73%CPU (6289major+4350minor)pagefaults 0swaps
rm -f linux1.tar 0.07user 0.55system 0:04.18elapsed 14%CPU (87major+13minor)pagefaults 0swaps
tar -czf linux1.tar.gz linux 598.07user 39.21system 10:44.11elapsed 98%CPU (7150major+2295minor)pagefaults 0swaps
parallel find : Thu Aug 6 21:35:05 CEST 1998 Thu Aug 6 21:44:03 CEST 1998
rm -rf linux 0.45user 4.55system 0:12.03elapsed 41%CPU (91major+19minor)pagefaults 0swaps Thu Aug 6 21:44:16 CEST 1998
* In short, start at 21:20:38, end at 21:44:16 * => total time 23'38'' * Another run: start at 22:21:02, end at 22:44:31 * => total time 23'29'' * ---------------------------- With option -fno-strength-reduce (edited):
Thu Aug 6 21:50:31 CEST 1998 Linux version 2.1.115 (root@xxxxxx.sony.de) (gcc version 2.7.2.3) #1 Thu Aug 6 14:33:14 CEST 1998 total: used: free: shared: buffers: cached: Mem: 15159296 7467008 7692288 7811072 757760 3055616 ... bogomips : 6.26
gunzip linux1.tar.gz 87.50user 22.03system 2:02.10elapsed 89%CPU (1604major+33minor)pagefaults 0swaps
tar -xf linux1.tar 21.11user 48.33system 1:36.65elapsed 71%CPU (6289major+4350minor)pagefaults 0swaps
rm -f linux1.tar 0.09user 0.43system 0:02.46elapsed 21%CPU (87major+13minor)pagefaults 0swaps
tar -czf linux1.tar.gz linux 601.94user 39.40system 10:48.13elapsed 98%CPU (7127major+2295minor)pagefaults 0swaps
parallel find : Thu Aug 6 22:05:02 CEST 1998 Thu Aug 6 22:13:57 CEST 1998
rm -rf linux 0.44user 4.85system 0:13.13elapsed 40%CPU (91major+19minor)pagefaults 0swaps Thu Aug 6 22:14:11 CEST 1998
* In short, start at 21:50:31, end at 22:14:11 * => total time 23'40'' ----------------------------
So, my benchmark is far to be perfect, but anyway better than compilling the kernel, and the option "-fno-strength-reduce" does not change anything on gcc 2.7.3 .
Bye, Etienne.
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