Athena P wrote: > Hi All > I tried compiling the toolchain with various optimisations and further down the line something always broke, so now I have an unoptimised toolchain and base. I selectively recompile certain apps for "performance boosts" (such as the example in this email). I think this is a good approach.
I was going to post this a few weeks ago but have been busy, so I'm just going to post the results without any nice graphics or tables (sorry). "I was wondering if anyone has done/is interested in running some comparisons of how different compiler flags affect performance/memory usage for various programs? Maybe this is off-topic but I only started getting interested in CFLAGS etc. while going through LFS... (and reading the Intel Compiler and optimising hints). I put together a shell script to automate the process of compiling and "measuring" performance for various CFLAGS. The attached output (values in bytes/seconds unless stated) is for lame compressing a large (150mb) wave file to mp3. The memory usage is from the Private values in /proc/PID/smaps and is the average of 3 runs (as are the times). I saw the lame example outputting to /dev/null somewhere on the web. While I did my best to make the results reliable (dropping into su mode (less bg procs) and averaging) I'm not really sure if smaps is a good value for memory usage... and lame is of course only a very specific example on specific (P4 3Ghz) hardware. It would be interesting to run these tests with icc and appropriate flags as well, as well as for other programs." I'm not attaching the shell script as it is a) Pretty ugly b) Written for the lame compile method. If there is interest I will rework it and post. Lame's default optimisations include -ffast-math, which seems to be the biggest performance booster in this case. Amadeus Sun Jan 28 19:20:41 CET 2007 lame --silent -h /home/amadeus/test.wav /dev/null ---------------------------------------- * (not specified so lame uses its own defaults) text data bss dec hex filename 424573 2088 203968 630629 99f65 frontend/lame Compiled file size: 458359 Private memory (kb): 1718 Real: 75.0033 User: 74.7767 Sys: 0.2 * -O2 text data bss dec hex filename 268881 2136 203968 474985 73f69 frontend/lame Compiled file size: 302570 Private memory (kb): 1640 Real: 79.9733 User: 79.7567 Sys: 0.19 * -O2 -march=pentium4 text data bss dec hex filename 263500 2132 203968 469600 72a60 frontend/lame Compiled file size: 296034 Private memory (kb): 1641 Real: 76.3167 User: 76.11 Sys: 0.173333 * -O2 -funroll-loops text data bss dec hex filename 400081 2136 203968 606185 93fe9 frontend/lame Compiled file size: 433512 Private memory (kb): 1717 Real: 78.07 User: 77.77 Sys: 0.27 * -O2 -march=pentium4 -funroll-loops text data bss dec hex filename 383004 2132 203968 589104 8fd30 frontend/lame Compiled file size: 415392 Private memory (kb): 1714 Real: 75.1833 User: 74.9433 Sys: 0.206667 * -O3 text data bss dec hex filename 310769 2136 203968 516873 7e309 frontend/lame Compiled file size: 342143 Private memory (kb): 1661 Real: 78.6433 User: 78.39 Sys: 0.22 * -O3 -march=pentium4 text data bss dec hex filename 305308 2132 203968 511408 7cdb0 frontend/lame Compiled file size: 336439 Private memory (kb): 1661 Real: 75.6267 User: 75.4067 Sys: 0.186667 * -O3 -funroll-loops text data bss dec hex filename 434033 2136 203968 640137 9c489 frontend/lame Compiled file size: 465183 Private memory (kb): 1738 Real: 79.2233 User: 78.9433 Sys: 0.253333 * -O3 -march=pentium4 -funroll-loops text data bss dec hex filename 417100 2132 203968 623200 98260 frontend/lame Compiled file size: 448631 Private memory (kb): 1718 Real: 75.49 User: 75.2233 Sys: 0.233333 * -Os text data bss dec hex filename 217389 2152 203968 423509 67655 frontend/lame Compiled file size: 250278 Private memory (kb): 1608 Real: 84.3333 User: 84.1167 Sys: 0.183333 * -Os -march=pentium4 text data bss dec hex filename 214957 2152 203968 421077 66cd5 frontend/lame Compiled file size: 247846 Private memory (kb): 1610 Real: 80.6533 User: 80.4333 Sys: 0.186667 * -Os -funroll-loops text data bss dec hex filename 327917 2152 203968 534037 82615 frontend/lame Compiled file size: 360676 Private memory (kb): 1685 Real: 80.74 User: 80.5167 Sys: 0.196667 * -Os -march=pentium4 -funroll-loops text data bss dec hex filename 317885 2152 203968 524005 7fee5 frontend/lame Compiled file size: 351940 Private memory (kb): 1666 Real: 77.9133 User: 77.7 Sys: 0.183333 Sun Jan 28 20:27:11 CET 2007 -- http://linuxfromscratch.org/mailman/listinfo/lfs-support FAQ: http://www.linuxfromscratch.org/lfs/faq.html Unsubscribe: See the above information page
