On Tue, 29 Mar 2005, Paul Jackson wrote: > Pekka wrote: > > (4) The cleanups Jesper and others are doing are to remove the > > _redundant_ NULL checks (i.e. it is now checked twice). > > Even such obvious changes as removing redundant checks doesn't > seem to ensure a performance improvement. Jesper Juhl posted > performance data for such changes in his microbenchmark a couple > of days ago. > > As I posted then, I could swear that his numbers show: > > > Just looking at the third run, it seems to me that "if (likely(p)) > > kfree(p);" beats a naked "kfree(p);" everytime, whether p is half > > NULL's, or very few NULL's, or almost all NULL's. > > Twice now I have asked Jesper to explain this strange result. > I've been kept busy with other things for a while and haven't had the time to reply to your emails, sorry. As I just said in another post I don't know how valid my numbers are, but I'll try and craft a few more tests to see if I can get some more solid results.
> > Maybe we should be following your good advice: > > > You don't know that until you profile! > > instead of continuing to make these code changes. > I'll gather some more numbers and post them along with any conclusions I believe can be drawn from them within a day or two, untill then I'll hold back on the patches... -- Jesper Juhl - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
