Some of you have seen this before. Just resending because
I based my next patch on top of this one.
Suggested by Linus: optimise a condition in the clear_p?d_range functions.
Results in one less conditional branch on i386 with gcc-3.4.4
Signed-off-by: Nick Piggin <[EMAIL PROTECTED]>
---
linux-2.6-npiggin/mm/memory.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff -puN mm/memory.c~mm-opt-cpr mm/memory.c
--- linux-2.6/mm/memory.c~mm-opt-cpr 2005-02-16 13:45:11.000000000 +1100
+++ linux-2.6-npiggin/mm/memory.c 2005-02-16 13:45:11.000000000 +1100
@@ -98,7 +98,8 @@ static inline void clear_pmd_range(struc
pmd_clear(pmd);
return;
}
- if (!(start & ~PMD_MASK) && !(end & ~PMD_MASK)) {
+ if (!((start | end) & ~PMD_MASK)) {
+ /* Only clear full, aligned ranges */
page = pmd_page(*pmd);
pmd_clear(pmd);
dec_page_state(nr_page_table_pages);
@@ -131,7 +132,8 @@ static inline void clear_pud_range(struc
addr = next;
} while (addr && (addr < end));
- if (!(start & ~PUD_MASK) && !(end & ~PUD_MASK)) {
+ if (!((start | end) & ~PUD_MASK)) {
+ /* Only clear full, aligned ranges */
pud_clear(pud);
pmd_free_tlb(tlb, __pmd);
}
@@ -162,7 +164,8 @@ static inline void clear_pgd_range(struc
addr = next;
} while (addr && (addr < end));
- if (!(start & ~PGDIR_MASK) && !(end & ~PGDIR_MASK)) {
+ if (!((start | end) & ~PGDIR_MASK)) {
+ /* Only clear full, aligned ranges */
pgd_clear(pgd);
pud_free_tlb(tlb, __pud);
}
_
