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authorChintan Pandya <cpandya@codeaurora.org>2018-06-07 17:06:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-07 17:34:35 -0700
commit82a2e924ff2c6accbc840dfa46c42b24da457a31 (patch)
treeac1421a481d921b4f3c0f748f450502e951da2b6
parent08994b24673b6ae33ee40fc3b5e265c6762848e4 (diff)
mm: vmalloc: clean up vunmap to avoid pgtable ops twice
vunmap does page table clear operations twice in the case when DEBUG_PAGEALLOC_ENABLE_DEFAULT is enabled. So, clean up the code as that is unintended. As a perf gain, we save few us. Below ftrace data was obtained while doing 1 MB of vmalloc/vfree on ARM64 based SoC *without* this patch applied. After this patch, we can save ~3 us (on 1 extra vunmap_page_range). CPU DURATION FUNCTION CALLS | | | | | | | 6) | __vunmap() { 6) | vmap_debug_free_range() { 6) 3.281 us | vunmap_page_range(); 6) + 45.468 us | } 6) 2.760 us | vunmap_page_range(); 6) ! 505.105 us | } [cpandya@codeaurora.org: v3] Link: http://lkml.kernel.org/r/1525176960-18408-1-git-send-email-cpandya@codeaurora.org Link: http://lkml.kernel.org/r/1523876342-10545-1-git-send-email-cpandya@codeaurora.org Signed-off-by: Chintan Pandya <cpandya@codeaurora.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Laura Abbott <labbott@redhat.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Florian Fainelli <f.fainelli@gmail.com> Cc: Yisheng Xie <xieyisheng1@huawei.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Wei Yang <richard.weiyang@gmail.com> Cc: Byungchul Park <byungchul.park@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/vmalloc.c29
1 files changed, 7 insertions, 22 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 63a5f502da08..12bd82e6554e 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -603,26 +603,6 @@ static void unmap_vmap_area(struct vmap_area *va)
vunmap_page_range(va->va_start, va->va_end);
}
-static void vmap_debug_free_range(unsigned long start, unsigned long end)
-{
- /*
- * Unmap page tables and force a TLB flush immediately if pagealloc
- * debugging is enabled. This catches use after free bugs similarly to
- * those in linear kernel virtual address space after a page has been
- * freed.
- *
- * All the lazy freeing logic is still retained, in order to minimise
- * intrusiveness of this debugging feature.
- *
- * This is going to be *slow* (linear kernel virtual address debugging
- * doesn't do a broadcast TLB flush so it is a lot faster).
- */
- if (debug_pagealloc_enabled()) {
- vunmap_page_range(start, end);
- flush_tlb_kernel_range(start, end);
- }
-}
-
/*
* lazy_max_pages is the maximum amount of virtual address space we gather up
* before attempting to purge with a TLB flush.
@@ -756,6 +736,9 @@ static void free_unmap_vmap_area(struct vmap_area *va)
{
flush_cache_vunmap(va->va_start, va->va_end);
unmap_vmap_area(va);
+ if (debug_pagealloc_enabled())
+ flush_tlb_kernel_range(va->va_start, va->va_end);
+
free_vmap_area_noflush(va);
}
@@ -1053,6 +1036,10 @@ static void vb_free(const void *addr, unsigned long size)
vunmap_page_range((unsigned long)addr, (unsigned long)addr + size);
+ if (debug_pagealloc_enabled())
+ flush_tlb_kernel_range((unsigned long)addr,
+ (unsigned long)addr + size);
+
spin_lock(&vb->lock);
/* Expand dirty range */
@@ -1142,7 +1129,6 @@ void vm_unmap_ram(const void *mem, unsigned int count)
BUG_ON(!PAGE_ALIGNED(addr));
debug_check_no_locks_freed(mem, size);
- vmap_debug_free_range(addr, addr+size);
if (likely(count <= VMAP_MAX_ALLOC)) {
vb_free(mem, size);
@@ -1499,7 +1485,6 @@ struct vm_struct *remove_vm_area(const void *addr)
va->flags |= VM_LAZY_FREE;
spin_unlock(&vmap_area_lock);
- vmap_debug_free_range(va->va_start, va->va_end);
kasan_free_shadow(vm);
free_unmap_vmap_area(va);