Benjamin LaHaise <[EMAIL PROTECTED]> writes: > On Fri, Mar 23, 2007 at 10:14:52AM +0000, Christoph Hellwig wrote: > > I think you're fixing the symptom here and not the cause. If calculating > > the virtual address of a page is so expensive on your setup it should > > define WANT_PAGE_VIRTUAL and we should always cache the virtual address > > in struct page. There's a lot more code, epecially in filesystems that's > > rather upset about a slow page_address. > > Andi shot that down when I brought it up a while ago, as it does show > up in profiles for networking and other code paths. His argument is that > the loss of memory is excessive. Personally, I think the benefits of a > 64 byte struct page on x86-64 outweigh the memory loss, as it means page > index to address translations are a simple shift.
At some point I had plans to make virt_to_page() etc. faster by using multiple look up tables that precompute some of the computation depending on the caller. But it might possibly cause more cache misses and the function didn't seem that time critical back then. But if you can really measure it so clearly it might be worth revisiting that. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
