On Wed, 14 Nov 2012 06:25:56 -0800 tip-bot for Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote: > mm: Count the number of pages affected in change_protection() > > This will be used by three kinds of purposes: > > - to optimize mprotect() > > - to speed up working set scanning for working set areas that > have not been touched > > - to more accurately scan per real working set > > No change in functionality from this patch. Seems simple, cheap and useful. A bit lacking in interface comments though. In particular, does the return value (which is in units of PAGE_SIZE pages) represent the number of pages which were inspected, or the number of pages which actually had their permissions modified? >From a quick look, it seems the answer is both. Or neither. If a page's protection was written to but unaltered, that counts as a "1". But if a pmd couldn't be locked via __pmd_trans_huge_lock(), that counts as a "0". Anyway, please have a think about it, and describe exactly what these return values mean? -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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