On 2010-Dec-23 04:48:19 +0800, Deano <de...@rattie.demon.co.uk> wrote: > modern CPU are float monsters indeed its >likely some things would be faster if converted to use the float ALU
_Some_ modern CPUs are good at FP, a lot aren't. The SPARC T-1 was particularly poor as it only had a single FPU. Likewise, performance in the x86 world is highly variable, depending on the vendor and core you pick. AFAIK, iA64 and PPC are consistently good - but neither are commonly found in conjunction with ZFS. You may also need to allow for software assist: Very few CPUs implement all of the IEEE FP standard in hardware and most (including SPARC) require software to implement parts of the standard. If your algorithm happens to make significant use of things other than normalised numbers and zero, your performance may be severely affected by the resultant traps and software assistance. Any use of floating point within the kernel also means changes to when FPU context is saved - and, unless this can be implemented lazily, it will adversely impact the cost of all context switches and potentially system calls. -- Peter Jeremy
pgphVXYz2zc3s.pgp
Description: PGP signature
_______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
