Hello,
Here's a patch to make it so empty PTEs are not added to mmu_gathers
(except the first one). It also reduces the number of unnecessary TLB
flushes.
This is useful on machines with sparse memory.
Tested on ia64 (Bjorn's latest 2.4.21-pre5) and i386 (2.4.21-pre7).
The patch applies cleanly against both 2.4.21 pre5 and pre7.
mh
-- Wild Open Source Inc. mort@wildopensource.comdiff -X /home/mort/diffex -uNr linux-2.4.21-pre5.pristine/include/asm-generic/tlb.h linux-2.4.21-pre5/include/asm-generic/tlb.h --- linux-2.4.21-pre5.pristine/include/asm-generic/tlb.h Fri Aug 2 18:39:45 2002 +++ linux-2.4.21-pre5/include/asm-generic/tlb.h Wed Apr 16 17:27:31 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 -X /home/mort/diffex -uNr linux-2.4.21-pre5.pristine/mm/memory.c linux-2.4.21-pre5/mm/memory.c --- linux-2.4.21-pre5.pristine/mm/memory.c Sun Mar 30 17:31:31 2003 +++ linux-2.4.21-pre5/mm/memory.c Wed Apr 16 18:11:18 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); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:21 EST