Messages in this thread | | | Date | Mon, 13 Mar 2006 20:36:43 +0100 | From | Sam Ravnborg <> | Subject | Re: [PATCH 18 of 20] ipath - kbuild infrastructure |
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On Mon, Mar 13, 2006 at 11:24:28AM -0800, Bryan O'Sullivan wrote: > 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? :-) Use the kernel settings. We cannot have this modified by each and every driver.
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