diff options
| author | Zachary Amsden <zach@vmware.com> | 2007-05-02 19:27:19 +0200 |
|---|---|---|
| committer | Andi Kleen <andi@basil.nowhere.org> | 2007-05-02 19:27:19 +0200 |
| commit | c2c1accd4b2f9c82fb89d40611c7f581948db255 (patch) | |
| tree | 0d4c6b8c2c53ff3d5657fdabe029f14f655fdac7 | |
| parent | df3624aa293dfa2d46089747d919711089a702eb (diff) | |
[PATCH] i386: pte clear optimization
When exiting from an address space, no special hypervisor notification of page
table updates needs to occur; direct page table hypervisors, such as Xen,
switch to another address space first (init_mm) and unprotects the page tables
to avoid the cost of trapping to the hypervisor for each pte_clear. Shadow
mode hypervisors, such as VMI and lhype don't need to do the extra work of
calling through paravirt-ops, and can just directly clear the page table
entries without notifiying the hypervisor, since all the page tables are about
to be freed.
So introduce native_pte_clear functions which bypass any paravirt-ops
notification. This results in a significant performance win for VMI and
removes some indirect calls from zap_pte_range.
Note the 3-level paging already had a native_pte_clear function, thus
demanding argument conformance and extra args for the 2-level definition.
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
| -rw-r--r-- | include/asm-i386/pgtable-2level.h | 5 | ||||
| -rw-r--r-- | include/asm-i386/pgtable.h | 2 |
2 files changed, 6 insertions, 1 deletions
diff --git a/include/asm-i386/pgtable-2level.h b/include/asm-i386/pgtable-2level.h index 781fe4bcc96..85d9005c0cd 100644 --- a/include/asm-i386/pgtable-2level.h +++ b/include/asm-i386/pgtable-2level.h @@ -36,6 +36,11 @@ static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd) #define pte_clear(mm,addr,xp) do { set_pte_at(mm, addr, xp, __pte(0)); } while (0) #define pmd_clear(xp) do { set_pmd(xp, __pmd(0)); } while (0) +static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *xp) +{ + *xp = __pte(0); +} + static inline pte_t native_ptep_get_and_clear(pte_t *xp) { return __pte(xchg(&xp->pte_low, 0)); diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h index e7ddd234130..00e97a9d367 100644 --- a/include/asm-i386/pgtable.h +++ b/include/asm-i386/pgtable.h @@ -344,7 +344,7 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, unsigned long pte_t pte; if (full) { pte = *ptep; - pte_clear(mm, addr, ptep); + native_pte_clear(mm, addr, ptep); } else { pte = ptep_get_and_clear(mm, addr, ptep); } |