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由 Thomas Gleixner 提交于
To avoid excessive 4k wise checks in the common case do a quick check first whether the requested new page protections conflict with a static protection area in the large page. If there is no conflict then the decision whether to preserve or to split the page can be made immediately. If the requested range covers the full large page, preserve it. Otherwise split it up. No point in doing a slow crawl in 4k steps. Before: 1G pages checked: 2 1G pages sameprot: 0 1G pages preserved: 0 2M pages checked: 538 2M pages sameprot: 466 2M pages preserved: 47 4K pages checked: 560642 4K pages set-checked: 7668 After: 1G pages checked: 2 1G pages sameprot: 0 1G pages preserved: 0 2M pages checked: 541 2M pages sameprot: 466 2M pages preserved: 47 4K pages checked: 514 4K pages set-checked: 7668 Signed-off-by: NThomas Gleixner <tglx@linutronix.de> Reviewed-by: NDave Hansen <dave.hansen@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Bin Yang <bin.yang@intel.com> Cc: Mark Gross <mark.gross@intel.com> Link: https://lkml.kernel.org/r/20180917143546.507259989@linutronix.de
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