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On Mon, 2006-03-13 at 19:10 +0100, Adrian Bunk wrote: > I'm still a bit surprised, since in the rest of the kernel we are even > going from -O2 to -Os for getting better performance. > > Robert said he wanted to post some numbers showing that -O3 is > measurably better for you [1], but I haven't seen them. I just ran some numbers. At large packet sizes, it doesn't matter what options we use, because we spend all of our time in __iowrite_copy32, which uses the string copy instructions. For small packets, my quick tests indicate that -Os gives about 5% *better* performance than -O3 (using gcc 4 on FC4). This is in line with what people have been finding in the kernel in general recently. So if I change that CFLAGS line from -O3 to -Os, are we in OK shape? :-) > > +_ipath_idstr:="PathScale $(shell date +%F)" > > +EXTRA_CFLAGS += -DIPATH_IDSTR='$(_ipath_idstr)' -DIPATH_KERN_TYPE=0 > >... > > UTS_VERSION is already available and printed at the top of dmesg. > I don't see the point in printing it a second time. Good point. The idstr stuff is for our out-of-tree drivers. Thanks, <b - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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