Hello,
Here's a patch to make it so empty PTEs are not added to mmu_gathers.
This is useful on machines with sparse memory. This has been tested on
ia64 and x86. Patch is against 2.4.21-bk.
mh
--
Wild Open Source Inc. [email protected]
# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
# ChangeSet 1.1209 -> 1.1210
# include/asm-generic/tlb.h 1.2 -> 1.3
# mm/memory.c 1.54 -> 1.55
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/05/12 [email protected] 1.1210
# Update the mmu_gathers code to avoid adding empty PTEs to mmu_gathers.
# --------------------------------------------
#
diff -Nru a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
--- a/include/asm-generic/tlb.h Mon May 12 13:14:23 2003
+++ b/include/asm-generic/tlb.h Mon May 12 13:14:23 2003
@@ -43,16 +43,16 @@
tlb->mm = mm;
/* Use fast mode if there is only one user of this mm (this process) */
- tlb->nr = (atomic_read(&(mm)->mm_users) == 1) ? ~0UL : 0UL;
+ tlb->nr = (atomic_read(&(mm)->mm_users) <= 1) ? ~0UL : 0UL;
return tlb;
}
-/* void tlb_remove_page(mmu_gather_t *tlb, pte_t *ptep, unsigned long addr)
+/* void tlb_remove_page(mmu_gather_t *tlb, struct page *page, pte_t *ptep, unsigned long addr)
* Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
* handling the additional races in SMP caused by other CPUs caching valid
* mappings in their TLBs.
*/
-#define tlb_remove_page(ctxp, pte, addr) do {\
+#define tlb_remove_page(ctxp, page, pte, addr) do {\
/* Handle the common case fast, first. */\
if ((ctxp)->nr == ~0UL) {\
pte_t __pte = *(pte);\
@@ -62,15 +62,19 @@
}\
if (!(ctxp)->nr) \
(ctxp)->start_addr = (addr);\
- (ctxp)->ptes[(ctxp)->nr++] = ptep_get_and_clear(pte);\
(ctxp)->end_addr = (addr) + PAGE_SIZE;\
+ (ctxp)->ptes[(ctxp)->nr] = ptep_get_and_clear(pte);\
+ if ((ctxp)->nr == 0 || (VALID_PAGE(page) && !PageReserved(page))) \
+ (ctxp)->nr++; \
if ((ctxp)->nr >= FREE_PTE_NR)\
tlb_finish_mmu((ctxp), 0, 0);\
} while (0)
/* tlb_finish_mmu
* Called at the end of the shootdown operation to free up any resources
- * that were required. The page talbe lock is still held at this point.
+ * that were required. The page table lock is still held at this point.
+ * Note that no TLB flushes are needed if there are no users of the mm
+ * context.
*/
static inline void tlb_finish_mmu(struct free_pte_ctx *ctx, unsigned long start, unsigned long end)
{
@@ -78,7 +82,8 @@
/* Handle the fast case first. */
if (ctx->nr == ~0UL) {
- flush_tlb_range(ctx->mm, start, end);
+ if (ctx->mm->mmap)
+ flush_tlb_range(ctx->mm, start, end);
return;
}
nr = ctx->nr;
@@ -101,7 +106,7 @@
#define tlb_gather_mmu(mm) (mm)
#define tlb_finish_mmu(tlb, start, end) flush_tlb_range(tlb, start, end)
-#define tlb_remove_page(tlb, ptep, addr) do {\
+#define tlb_remove_page(tlb, page, ptep, addr) do {\
pte_t __pte = *(ptep);\
pte_clear(ptep);\
__free_pte(__pte);\
diff -Nru a/mm/memory.c b/mm/memory.c
--- a/mm/memory.c Mon May 12 13:14:23 2003
+++ b/mm/memory.c Mon May 12 13:14:23 2003
@@ -318,7 +318,7 @@
if (VALID_PAGE(page) && !PageReserved(page))
freed ++;
/* This will eventually call __free_pte on the pte. */
- tlb_remove_page(tlb, ptep, address + offset);
+ tlb_remove_page(tlb, page, ptep, address + offset);
} else {
free_swap_and_cache(pte_to_swp_entry(pte));
pte_clear(ptep);
On Mon, 12 May 2003, Martin Hicks wrote:
> Here's a patch to make it so empty PTEs are not added to mmu_gathers.
> This is useful on machines with sparse memory. This has been tested on
> ia64 and x86. Patch is against 2.4.21-bk.
The patch looks good. We will still flush everything in the
TLB that we used to flush before, but by not using struct
page in the buffer for non-existant and reserved pages we can
flush the TLB in much larger intervals.
Marcelo, could you please apply this patch for 2.4.22-pre ?
(I'll keep a copy here and will resend it to you if needed)