Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
Marko Karppinen writes: GCC sets __FAST_MATH__ even if you counter a -ffast-math with the negating flags above. This means that it is not currently possible to use the -fast flag when compiling PostgreSQL at all. Instead, you have to go through all the flags Apple is setting and only pass on those that don't break pg. That sounds perfectly reasonable to me. Why should we develop elaborate workarounds for compiler flags that are known to create broken code? I also want to point out that I'm getting kind of tired of developing more and more workarounds for sloppy Apple engineering. -- Peter Eisentraut [EMAIL PROTECTED] ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
On 8.10.2003, at 21:31, Bruce Momjian wrote: Well, this is really embarassing. I can't imagine why we would not set at least -O on all platforms. Looking at the template files, I see these have no optimization set: darwin Regarding Darwin optimizations, Apple has introduced a -fast flag in their GCC 3.3 version that they recommend when compiling code for their new G5 systems. Because of this, I foresee a lot of people defining CFLAGS=-fast on their systems. This is problematic for PostgreSQL, however, since the -fast flag is the equivalent of: -O3 -falign-loops-max-skip=15 -falign-jumps-max-skip=15 -falign-loops=16 -falign-jumps=16 -falign-functions=16 -malign-natural -ffast-math -fstrict-aliasing -frelax-aliasing -fgcse-mem-alias -funroll-loops -floop-transpose -floop-to-memset -finline-floor -mcpu=G5 -mpowerpc64 -mpowerpc-gpopt -mtune=G5 -fsched-interblock -fload-after-store --param max-gcse-passes=3 -fno-gcse-sm -fgcse-loop-depth -funit-at-a-time -fcallgraph-inlining -fdisable-typechecking-for-spec At least the --fast-math part causes problems, seeing that PostgreSQL actually checks for the __FAST_MATH__ macro to make sure that it isn't turned on. There might be other problems with Apple's flags, but I think that the __FAST_MATH__ check should be altered. As you know, setting --fast-math in GCC is the equivalent of setting -fno-math-errno, -funsafe-math-optimizations, -fno-trapping-math, -ffinite-math-only and -fno-signaling-nans. What really should be done, I think, is adding the opposites of these flags (-fmath-errno, -fno-unsafe-math-optimizations, -ftrapping_math, -fno-finite-math-only and -fsignaling-nans) to the command line if __FAST_MATH__ is detected. This would allow people to use CFLAGS=-fast on their G5s, beat some Xeon speed records, and not worry about esoteric IEEE math standards. What do you guys think? GCC sets __FAST_MATH__ even if you counter a -ffast-math with the negating flags above. This means that it is not currently possible to use the -fast flag when compiling PostgreSQL at all. Instead, you have to go through all the flags Apple is setting and only pass on those that don't break pg. mk ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
Bruce Momjian [EMAIL PROTECTED] writes: OK, patch attached and applied. It centralizes the optimization defaults into configure.in, rather than having CFLAGS= in the template files. I think there's a problem here: + # configure sets CFLAGS to -O2 for gcc, so this is only for non-gcc + if test x$CFLAGS = x; then + CFLAGS=-O + fi if test $enable_debug = yes test $ac_cv_prog_cc_g = yes; then CFLAGS=$CFLAGS -g fi since this will cause configure --enable-debug to default to selecting CFLAGS=-O -g for non-gcc compilers. On a lot of compilers that combination does not work, and will generate tons of useless warnings. I think it might be better to do if test $enable_debug = yes test $ac_cv_prog_cc_g = yes; then CFLAGS=$CFLAGS -g + else + # configure sets CFLAGS to -O2 for gcc, so this is only for non-gcc + if test x$CFLAGS = x; then + CFLAGS=-O + fi fi regards, tom lane ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
Done as you suggested. --- Tom Lane wrote: Bruce Momjian [EMAIL PROTECTED] writes: OK, patch attached and applied. It centralizes the optimization defaults into configure.in, rather than having CFLAGS= in the template files. I think there's a problem here: + # configure sets CFLAGS to -O2 for gcc, so this is only for non-gcc + if test x$CFLAGS = x; then + CFLAGS=-O + fi if test $enable_debug = yes test $ac_cv_prog_cc_g = yes; then CFLAGS=$CFLAGS -g fi since this will cause configure --enable-debug to default to selecting CFLAGS=-O -g for non-gcc compilers. On a lot of compilers that combination does not work, and will generate tons of useless warnings. I think it might be better to do if test $enable_debug = yes test $ac_cv_prog_cc_g = yes; then CFLAGS=$CFLAGS -g + else + # configure sets CFLAGS to -O2 for gcc, so this is only for non-gcc + if test x$CFLAGS = x; then + CFLAGS=-O + fi fi regards, tom lane -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
On Wed, Oct 08, 2003 at 02:31:29PM -0400, Bruce Momjian wrote: Well, this is really embarassing. I can't imagine why we would not set at least -O on all platforms. Looking at the template files, I see these have no optimization set: I think gcc _used_ to generate bad code on SPARC if you set any optimisation. We tested it on Sol7 with gcc 2.95 more than a year ago, and tried various settings. -O2 worked, but other items were really bad. Some of them would pass regression but cause strange behaviour, random coredumps, c. A little digging demonstrated that anything beyond -O2 just didn't work for gcc at the time. A -- Andrew Sullivan 204-4141 Yonge Street Afilias CanadaToronto, Ontario Canada [EMAIL PROTECTED] M2P 2A8 +1 416 646 3304 x110 ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
On Wed, 8 Oct 2003, Neil Conway wrote: ISTM the most legitimate reason for not enabling compilater optimizations on a given compiler/OS/architecture combination is might cause compiler errors / bad code generation. Can we get these optimizations enabled in time for the next 7.4 beta? It might also be good to add an item in the release notes about it. -Neil I just ran make check for sun with gcc -O2 and suncc -fast and both passed. We'll need other arguments to suncc to supress some warnings, etc. (-fast generates a warning for every file compiled telling you it will only run on ultrasparc machines) -- Jeff Trout [EMAIL PROTECTED] http://www.jefftrout.com/ http://www.stuarthamm.net/ ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
Peter Eisentraut wrote: Bruce Momjian writes: Well, this is really embarassing. I can't imagine why we would not set at least -O on all platforms. Looking at the template files, I see these have no optimization set: freebsd (non-alpha) I'm wondering what that had in mind: http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/template/freebsd.diff?r1=1.10r2=1.11 I was wondering that myself. I think the idea was that we already do -O2 in configure if it is gcc, so why do it in the template files. What is killing us is the CFLAGS= lines in the configuration files. -- Bruce Momjian| http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
Well, this is really embarassing. I can't imagine why we would not set at least -O on all platforms. Looking at the template files, I see these have no optimization set: freebsd (non-alpha) I'm wondering what that had in mind: http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/template/freebsd.diff?r1=1.10r2=1.11 When I used to build pgsql on freebsd/alpha, I would get heaps of GCC warnings saying 'optimisations for the alpha are broken'. I can't remember if that meant anything more than just -O or not though. Chris ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [HACKERS] [PERFORM] Sun performance - Major discovery!
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