Messages in this thread | | | Date | Thu, 03 Jul 2003 19:46:24 -0700 | From | "Martin J. Bligh" <> | Subject | Re: Overhead of highpte |
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> On Wed, 2003-07-02 at 15:53, Martin J. Bligh wrote: >> Some people were saying they couldn't see an overhead with highpte. >> Seems pretty obvious to me still. It should help *more* on the NUMA >> box, as PTEs become node-local. >> >> The kmap_atomic is, of course, perfectly understandable. The increase >> in the rmap functions is a bit of a mystery to me. >> >> M. >> >> Kernbench: (make -j vmlinux, maximal tasks) >> Elapsed System User CPU >> 2.5.73-mm3 45.38 114.91 565.81 1497.75 >> 2.5.73-mm3-highpte 46.54 130.41 566.84 1498.00 > > OK, let's add to the mystery. Here's my run, on virtually the same > hardware except, I don't do a bzImage. bzImage is pretty useless > because I don't want to benchmark gzip, so I just do vmlinux. My times > should be _faster_ than yours, right?
I do vmlinux as well.
> Elapsed: User: System: CPU: > 2.5.73-mjb2 77.008s 937.756s 90s 1334% > 2.5.73-mjb2-highpte 76.756s 935.464s 93.116s 1339% > > Yeah, system time goes up. Something funky is going on. We should have > the same machines, except that I have twice the RAM, right? What kind > of fs are you doing your tests on? I'm doing ramfs.
ext2.
I suspect the problem is that your gcc is such a slow piece of shit, you're totally userspace bound. Try 2.95 (just move the /usr/bin/gcc symlink on debian).
M.
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