![Christoph Lameter](/assets/img/avatar_default.png)
__get_cpu_var() is used for multiple purposes in the kernel source. One of them is address calculation via the form &__get_cpu_var(x). This calculates the address for the instance of the percpu variable of the current processor based on an offset. Other use cases are for storing and retrieving data from the current processors percpu area. __get_cpu_var() can be used as an lvalue when writing data or on the right side of an assignment. __get_cpu_var() is defined as : #define __get_cpu_var(var) (*this_cpu_ptr(&(var))) __get_cpu_var() always only does an address determination. However, store and retrieve operations could use a segment prefix (or global register on other platforms) to avoid the address calculation. this_cpu_write() and this_cpu_read() can directly take an offset into a percpu area and use optimized assembly code to read and write per cpu variables. This patch converts __get_cpu_var into either an explicit address calculation using this_cpu_ptr() or into a use of this_cpu operations that use the offset. Thereby address calculations are avoided and less registers are used when code is generated. At the end of the patch set all uses of __get_cpu_var have been removed so the macro is removed too. The patch set includes passes over all arches as well. Once these operations are used throughout then specialized macros can be defined in non -x86 arches as well in order to optimize per cpu access by f.e. using a global register that may be set to the per cpu base. Transformations done to __get_cpu_var() 1. Determine the address of the percpu instance of the current processor. DEFINE_PER_CPU(int, y); int *x = &__get_cpu_var(y); Converts to int *x = this_cpu_ptr(&y); 2. Same as #1 but this time an array structure is involved. DEFINE_PER_CPU(int, y[20]); int *x = __get_cpu_var(y); Converts to int *x = this_cpu_ptr(y); 3. Retrieve the content of the current processors instance of a per cpu variable. DEFINE_PER_CPU(int, y); int x = __get_cpu_var(y) Converts to int x = __this_cpu_read(y); 4. Retrieve the content of a percpu struct DEFINE_PER_CPU(struct mystruct, y); struct mystruct x = __get_cpu_var(y); Converts to memcpy(&x, this_cpu_ptr(&y), sizeof(x)); 5. Assignment to a per cpu variable DEFINE_PER_CPU(int, y) __get_cpu_var(y) = x; Converts to __this_cpu_write(y, x); 6. Increment/Decrement etc of a per cpu variable DEFINE_PER_CPU(int, y); __get_cpu_var(y)++ Converts to __this_cpu_inc(y) Cc: sparclinux@vger.kernel.org Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
244 lines
4.8 KiB
C
244 lines
4.8 KiB
C
/* arch/sparc64/mm/tlb.c
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*
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* Copyright (C) 2004 David S. Miller <davem@redhat.com>
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*/
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#include <linux/kernel.h>
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#include <linux/percpu.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/preempt.h>
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#include <asm/pgtable.h>
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#include <asm/pgalloc.h>
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#include <asm/tlbflush.h>
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#include <asm/cacheflush.h>
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#include <asm/mmu_context.h>
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#include <asm/tlb.h>
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/* Heavily inspired by the ppc64 code. */
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static DEFINE_PER_CPU(struct tlb_batch, tlb_batch);
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void flush_tlb_pending(void)
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{
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struct tlb_batch *tb = &get_cpu_var(tlb_batch);
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struct mm_struct *mm = tb->mm;
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if (!tb->tlb_nr)
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goto out;
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flush_tsb_user(tb);
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if (CTX_VALID(mm->context)) {
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if (tb->tlb_nr == 1) {
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global_flush_tlb_page(mm, tb->vaddrs[0]);
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} else {
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#ifdef CONFIG_SMP
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smp_flush_tlb_pending(tb->mm, tb->tlb_nr,
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&tb->vaddrs[0]);
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#else
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__flush_tlb_pending(CTX_HWBITS(tb->mm->context),
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tb->tlb_nr, &tb->vaddrs[0]);
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#endif
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}
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}
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tb->tlb_nr = 0;
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out:
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put_cpu_var(tlb_batch);
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}
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void arch_enter_lazy_mmu_mode(void)
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{
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struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
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tb->active = 1;
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}
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void arch_leave_lazy_mmu_mode(void)
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{
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struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
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if (tb->tlb_nr)
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flush_tlb_pending();
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tb->active = 0;
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}
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static void tlb_batch_add_one(struct mm_struct *mm, unsigned long vaddr,
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bool exec)
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{
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struct tlb_batch *tb = &get_cpu_var(tlb_batch);
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unsigned long nr;
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vaddr &= PAGE_MASK;
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if (exec)
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vaddr |= 0x1UL;
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nr = tb->tlb_nr;
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if (unlikely(nr != 0 && mm != tb->mm)) {
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flush_tlb_pending();
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nr = 0;
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}
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if (!tb->active) {
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flush_tsb_user_page(mm, vaddr);
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global_flush_tlb_page(mm, vaddr);
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goto out;
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}
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if (nr == 0)
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tb->mm = mm;
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tb->vaddrs[nr] = vaddr;
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tb->tlb_nr = ++nr;
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if (nr >= TLB_BATCH_NR)
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flush_tlb_pending();
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out:
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put_cpu_var(tlb_batch);
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}
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void tlb_batch_add(struct mm_struct *mm, unsigned long vaddr,
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pte_t *ptep, pte_t orig, int fullmm)
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{
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if (tlb_type != hypervisor &&
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pte_dirty(orig)) {
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unsigned long paddr, pfn = pte_pfn(orig);
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struct address_space *mapping;
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struct page *page;
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if (!pfn_valid(pfn))
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goto no_cache_flush;
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page = pfn_to_page(pfn);
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if (PageReserved(page))
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goto no_cache_flush;
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/* A real file page? */
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mapping = page_mapping(page);
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if (!mapping)
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goto no_cache_flush;
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paddr = (unsigned long) page_address(page);
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if ((paddr ^ vaddr) & (1 << 13))
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flush_dcache_page_all(mm, page);
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}
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no_cache_flush:
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if (!fullmm)
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tlb_batch_add_one(mm, vaddr, pte_exec(orig));
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}
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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static void tlb_batch_pmd_scan(struct mm_struct *mm, unsigned long vaddr,
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pmd_t pmd)
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{
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unsigned long end;
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pte_t *pte;
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pte = pte_offset_map(&pmd, vaddr);
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end = vaddr + HPAGE_SIZE;
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while (vaddr < end) {
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if (pte_val(*pte) & _PAGE_VALID) {
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bool exec = pte_exec(*pte);
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tlb_batch_add_one(mm, vaddr, exec);
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}
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pte++;
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vaddr += PAGE_SIZE;
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}
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pte_unmap(pte);
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}
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void set_pmd_at(struct mm_struct *mm, unsigned long addr,
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pmd_t *pmdp, pmd_t pmd)
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{
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pmd_t orig = *pmdp;
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*pmdp = pmd;
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if (mm == &init_mm)
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return;
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if ((pmd_val(pmd) ^ pmd_val(orig)) & _PAGE_PMD_HUGE) {
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if (pmd_val(pmd) & _PAGE_PMD_HUGE)
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mm->context.huge_pte_count++;
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else
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mm->context.huge_pte_count--;
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/* Do not try to allocate the TSB hash table if we
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* don't have one already. We have various locks held
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* and thus we'll end up doing a GFP_KERNEL allocation
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* in an atomic context.
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*
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* Instead, we let the first TLB miss on a hugepage
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* take care of this.
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*/
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}
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if (!pmd_none(orig)) {
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addr &= HPAGE_MASK;
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if (pmd_trans_huge(orig)) {
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pte_t orig_pte = __pte(pmd_val(orig));
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bool exec = pte_exec(orig_pte);
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tlb_batch_add_one(mm, addr, exec);
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tlb_batch_add_one(mm, addr + REAL_HPAGE_SIZE, exec);
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} else {
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tlb_batch_pmd_scan(mm, addr, orig);
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}
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}
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}
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void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
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pmd_t *pmdp)
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{
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pmd_t entry = *pmdp;
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pmd_val(entry) &= ~_PAGE_VALID;
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set_pmd_at(vma->vm_mm, address, pmdp, entry);
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flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
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}
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void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
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pgtable_t pgtable)
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{
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struct list_head *lh = (struct list_head *) pgtable;
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assert_spin_locked(&mm->page_table_lock);
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/* FIFO */
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if (!pmd_huge_pte(mm, pmdp))
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INIT_LIST_HEAD(lh);
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else
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list_add(lh, (struct list_head *) pmd_huge_pte(mm, pmdp));
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pmd_huge_pte(mm, pmdp) = pgtable;
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}
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pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
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{
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struct list_head *lh;
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pgtable_t pgtable;
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assert_spin_locked(&mm->page_table_lock);
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/* FIFO */
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pgtable = pmd_huge_pte(mm, pmdp);
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lh = (struct list_head *) pgtable;
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if (list_empty(lh))
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pmd_huge_pte(mm, pmdp) = NULL;
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else {
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pmd_huge_pte(mm, pmdp) = (pgtable_t) lh->next;
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list_del(lh);
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}
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pte_val(pgtable[0]) = 0;
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pte_val(pgtable[1]) = 0;
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return pgtable;
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}
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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