Hi, I could not say for sure the difference between sin and sinf (for example) on Suse but the performance ratio I had on 32 bits, stayed the same on 64 bits. This is why I was surprised to get impressive slowness when moving to debian :( Thanks for pointing out the Suse patch : as we only have Suse or Debian at work I could not do more comparisons.
How about including patches from OpenSuse ? Is it possible as a quick workaround? Thanks for your help. Jerome On Sunday 07 March 2010, you wrote: > On Sun, Mar 07, 2010 at 04:17:08PM +0100, Aurelien Jarno wrote: > > On Sat, Mar 06, 2010 at 11:42:51AM +0100, Jerome Vizcaino wrote: > > > Package: libc6 > > > Version: 2.10.2-6 > > > Severity: normal > > > > > > Hi, > > > > > > After many tests and research I've come to the conclusion that the > > > float variants of > > > sin/cos (and maybe others) are anormaly slow Debian amd64. > > > The performance loss is really impressive (around 8 to 9 times slower). > > > I've attached the prog used to make my experiments and used it in the > > > following cases. > > > > > > + Lenny-amd64: sinf/cosf is really slow > > > + Lenny-i386: float performance is ok (faster than the cos/sin using > > > double) + Sid-amd64: sinf/cosf slow > > > + Lenny-amd64 using lenny-i386 binary and 32bits libs: float > > > performance is OK. > > > > On amd64, only sincos has an optimized version, sincosf is using the > > generic C implementation. On i386, there are optimized version of both > > sincos and sincosf > > > > > + OpenSuse 64 bits (10.3 and 11.1): using the binary compiled on > > > lenny-amd64, the tests run fine ! > > > => The problem is not compiler related. > > > > > > There seems to be a problem with the way libm is compiled for the amd64 > > > architecture on Debian. > > > This is why the OpenSuse test was run: the problem is somewhere in the > > > compile chain or debian specific patches. > > > > The problem is clearly not Debian specific, and is also present > > upstream. OpenSuse is probably using a patch to workaround the problem. > > This is confirmed, there using an AMD version of the libm library on > x86_64, still coded in C for the sincosf function. > > A quick an dirty implementation of sincosf in x86_64 assembly gives me a > speed around 4% slower than sincos. What kind of performance ratio do > you get on SuSe? > > The solution seems to write each *f function in x86_64 assembly, but > that'll probably take time. > -- To UNSUBSCRIBE, email to debian-glibc-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/201003071943.46266.vizcaino_jer...@yahoo.fr
