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a=Wb1JkmetP80A:10 a=GoEa3M9JfhUA:10 a=i0EeH86SAAAA:8 a=m8Hz9ToHBu6fQcDdDGwA:9 a=CjuIK1q_8ugA:10 On Wed, Jul 30, 2025 at 05:19:05PM +0800, Zhang Qilong wrote: > Attempt to map aligned to huge page size for private mapping which > could achieve performance gains, the mprot_tw4m in libMicro average > execution time on arm64: > - Test case: mprot_tw4m > - Before the patch: 22 us > - After the patch: 17 us > > Signed-off-by: Zhang Qilong > --- > v2: > - Add comments on code suggested by Lorenzo > - Use IS_ENABLED to check THP config > > drivers/char/mem.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/char/mem.c b/drivers/char/mem.c > index 48839958b0b1..c27cc89bd02d 100644 > --- a/drivers/char/mem.c > +++ b/drivers/char/mem.c > @@ -525,11 +525,18 @@ static unsigned long get_unmapped_area_zero(struct file *file, > * so as not to confuse shmem with our handle on "/dev/zero". > */ > return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags); > } > > - /* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */ > + /* > + * Otherwise flags & MAP_PRIVATE: with no shmem object beneath it, > + * attempt to map aligned to huge page size if possible, otherwise we > + * fall back to system page size mappings. > + */ Nit, but put a space after this as it aplies to both blocks. > + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > + return thp_get_unmapped_area(file, addr, len, pgoff, flags); As mentioned by Matthew, and as requested originally, please make this an #ifdef / #else. You might then want to factor out the #ifdef CONFIG_MMU (gross) at a higher level. I'm sick of us bending over backwards for museum piece (or should be) nommu but anyway. Something like #ifdef CONFIG_MMU static unsigned long get_unmapped_area_zero(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { return -ENOSYS; } #else ... It's ugly but unfortunately I think necessary. > + > return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); > #else > return -ENOSYS; > #endif > } > -- > 2.43.0 > Thanks, Lorenzo