Messages in this thread | | | Date | Tue, 27 Oct 2015 19:13:51 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] mutex: make mutex_lock_nested an inline function |
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* Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:
> On Thu, Oct 22, 2015 at 05:09:59PM +0200, Peter Zijlstra wrote: > > Hmm, I was sure I send a reply, but I cannot even find it in my own sent > > folder so who knows. > > > > My current preference is to keep the thing a macro and work around it in > > the usage site because while these warns are annoying, they're at least > > visible. Whereas, with an inline, code bloat is entirely silent. Even if > > the sites you found are harmless, there's no saying what the future will > > bring etc.. > > I agree - we've got way too many inline functions already. My biggest annoyance > in that respect is the asm-generic dma_map_single() implementation that we're > now forced to use on ARM, which results in quite a large chunk of code at every > callsite. > > The problem there is that when you have drivers which do something like: > > dma = dma_map_single(dev, page_address(page), size, dir); > > you end up with code which converts the struct page to a virtual address, and > then you end up with code in the dma_map_single() inline function which then > converts it back to a struct page + offset - none of which, with modern ARM > kernels, the compiler has a hope in hell of optimising. > > So we end up with all that junk at every single dma_map_single() callsite. If > dma_map_single() were a library function, it would be a lot smaller since we'd > only have one copy of the complex virt->struct page conversion.
Should be pretty easy to fix, once you know which inline functions hurt.
Thanks,
Ingo
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