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For example, the zap path > calls it for every leaf page table entry. > > Rewrite the helper function in a branchless manner to eliminate the risk > of CPU branch misprediction. > > Signed-off-by: Kiryl Shutsemau > Reviewed-by: Muchun Song > --- > include/linux/page-flags.h | 27 +++++++++++++++++---------- > 1 file changed, 17 insertions(+), 10 deletions(-) LGTM. And it fixed the issue in patch 10. Reviewed-by: Zi Yan > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index f89702e101e8..95ac963b78af 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -224,25 +224,32 @@ static __always_inline bool compound_info_has_mask(void) > static __always_inline unsigned long _compound_head(const struct page *page) > { > unsigned long info = READ_ONCE(page->compound_info); > + unsigned long mask; > + > + if (!compound_info_has_mask()) { > + /* Bit 0 encodes PageTail() */ > + if (info & 1) > + return info - 1; > > - /* Bit 0 encodes PageTail() */ > - if (!(info & 1)) > return (unsigned long)page; Here, info & 1 check now is guarded by compound_info_has_mask(), so the issue I mentioned in Patch 10 is gone. > - > - /* > - * If compound_info_has_mask() is false, the rest of compound_info is > - * the pointer to the head page. > - */ > - if (!compound_info_has_mask()) > - return info - 1; > + } Best Regards, Yan, Zi