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Date: Tue, 26 Feb 2008 16:29:58 +0100 From: Miklos Szeredi <miklos@...redi.hu> To: a.p.zijlstra@...llo.nl CC: neilb@...e.de, akpm@...ux-foundation.org, torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, netdev@...r.kernel.org, trond.myklebust@....uio.no Subject: Re: [PATCH 00/28] Swap over NFS -v16 > > mm-page_file_methods.patch > > > > This makes page_offset and others more expensive by adding a > > conditional jump to a function call that is not usually made. > > > > Why do swap pages have a different index to everyone else? > > Because the page->index of an anonymous page is related to its (anon)vma > so that it satisfies the constraints for vm_normal_page(). > > The index in the swap file it totally unrelated and quite random. Hence > the swap-cache uses page->private to store it in. Yeah, and putting the condition into page_offset() will confuse code which uses it for finding the offset in the VMA or in a tmpfs file. So why not just have a separate page_swap_offset() function, used exclusively by swap_in/out()? Miklos -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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