| Date | Tue, 5 May 2015 19:50:58 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 000/208] big x86 FPU code rewrite |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Tue, May 5, 2015 at 9:23 AM, Ingo Molnar <mingo@kernel.org> wrote: > > 83 files changed, 3742 insertions(+), 2841 deletions(-) > > How much of this is just the added instrumentation? [...]
Half of it is that, plus a lot of comments.
> [...] Because that's almost a thousand new lines, which makes me > unhappy. The *last* thing we want is to make this thing bigger. > [...]
So Boris suggested that I should move fpu/measure.c out of the FPU code anyway, which is fair enough, as it measures a lot of other low level details as well. Consider it done.
With that taken out, the diffstat comes down to:
81 files changed, 3409 insertions(+), 3055 deletions(-)
That's mostly 400 new lines of comments all around the FPU code, plus a bit of extra headers due to the split-up modules (50-100 lines maybe).
> [...] I'm not convinced it's worth it adding some performance debug > code that doesn't really add any new information, and could be done > outside the kernel as just an independent module instead.
Code size difference (with debugging off) on an x86-64 defconfig-ish kernel:
text data bss filename
15030376 2574976 1634304 vmlinux.before 15023690 2578648 1634304 vmlinux.after
The runtime size of the kernel got smaller by 7K.
Considering that arch/x86/kernel/fpu/built-in.o is only 13K that's quite significant.
Thanks,
Ingo
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