提交 8892d854 编写于 作者: A Anton Ivanov 提交者: Richard Weinberger

um: Avoid marking pages with "changed protection"

Changing protection is a very high cost operation in UML
because in addition to an extra syscall it also interrupts
mmap merge sequences generated by the tlb.

While the condition is not particularly common it is worth
avoiding.
Signed-off-by: NAnton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: NRichard Weinberger <richard@nod.at>
上级 38e3cbd9
无相关合并请求
......@@ -197,12 +197,17 @@ static inline pte_t pte_mkold(pte_t pte)
static inline pte_t pte_wrprotect(pte_t pte)
{
pte_clear_bits(pte, _PAGE_RW);
if (likely(pte_get_bits(pte, _PAGE_RW)))
pte_clear_bits(pte, _PAGE_RW);
else
return pte;
return(pte_mknewprot(pte));
}
static inline pte_t pte_mkread(pte_t pte)
{
if (unlikely(pte_get_bits(pte, _PAGE_USER)))
return pte;
pte_set_bits(pte, _PAGE_USER);
return(pte_mknewprot(pte));
}
......@@ -221,6 +226,8 @@ static inline pte_t pte_mkyoung(pte_t pte)
static inline pte_t pte_mkwrite(pte_t pte)
{
if (unlikely(pte_get_bits(pte, _PAGE_RW)))
return pte;
pte_set_bits(pte, _PAGE_RW);
return(pte_mknewprot(pte));
}
......
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