From edd898181e2f6f0969c08e1dfe2b7cdf902b9b33 Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Thu, 22 Dec 2022 20:00:20 +0100 Subject: mm: vmalloc: avoid calling __find_vmap_area() twice in __vunmap() Currently the __vunmap() path calls __find_vmap_area() twice. Once on entry to check that the area exists, then inside the remove_vm_area() function which also performs a new search for the VA. In order to improvie it from a performance point of view we split remove_vm_area() into two new parts: - find_unlink_vmap_area() that does a search and unlink from tree; - __remove_vm_area() that removes without searching. In this case there is no any functional change for remove_vm_area() whereas vm_remove_mappings(), where a second search happens, switches to the __remove_vm_area() variant where the already detached VA is passed as a parameter, so there is no need to find it again. Performance wise, i use test_vmalloc.sh with 32 threads doing alloc free on a 64-CPUs-x86_64-box: perf without this patch: - 31.41% 0.50% vmalloc_test/10 [kernel.vmlinux] [k] __vunmap - 30.92% __vunmap - 17.67% _raw_spin_lock native_queued_spin_lock_slowpath - 12.33% remove_vm_area - 11.79% free_vmap_area_noflush - 11.18% _raw_spin_lock native_queued_spin_lock_slowpath 0.76% free_unref_page perf with this patch: - 11.35% 0.13% vmalloc_test/14 [kernel.vmlinux] [k] __vunmap - 11.23% __vunmap - 8.28% find_unlink_vmap_area - 7.95% _raw_spin_lock 7.44% native_queued_spin_lock_slowpath - 1.93% free_vmap_area_noflush - 0.56% _raw_spin_lock 0.53% native_queued_spin_lock_slowpath 0.60% __vunmap_range_noflush __vunmap() consumes around ~20% less CPU cycles on this test. Also, switch from find_vmap_area() to find_unlink_vmap_area() to prevent a double access to the vmap_area_lock: one for finding area, second time is for unlinking from a tree. [urezki@gmail.com: switch to find_unlink_vmap_area() in vm_unmap_ram()] Link: https://lkml.kernel.org/r/20221222190022.134380-2-urezki@gmail.com Link: https://lkml.kernel.org/r/20221222190022.134380-1-urezki@gmail.com Signed-off-by: Uladzislau Rezki (Sony) Reported-by: Roman Gushchin Reviewed-by: Lorenzo Stoakes Cc: Baoquan He Cc: Christoph Hellwig Cc: Matthew Wilcox (Oracle) Cc: Nicholas Piggin Cc: Oleksiy Avramchenko Cc: Christoph Hellwig Signed-off-by: Andrew Morton --- mm/vmalloc.c | 79 ++++++++++++++++++++++++++++++++++++------------------------ 1 file changed, 48 insertions(+), 31 deletions(-) (limited to 'mm/vmalloc.c') diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 10fe83c24436..476ccbffb208 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1815,9 +1815,9 @@ static void drain_vmap_area_work(struct work_struct *work) } /* - * Free a vmap area, caller ensuring that the area has been unmapped - * and flush_cache_vunmap had been called for the correct range - * previously. + * Free a vmap area, caller ensuring that the area has been unmapped, + * unlinked and flush_cache_vunmap had been called for the correct + * range previously. */ static void free_vmap_area_noflush(struct vmap_area *va) { @@ -1825,9 +1825,8 @@ static void free_vmap_area_noflush(struct vmap_area *va) unsigned long va_start = va->va_start; unsigned long nr_lazy; - spin_lock(&vmap_area_lock); - unlink_va(va, &vmap_area_root); - spin_unlock(&vmap_area_lock); + if (WARN_ON_ONCE(!list_empty(&va->list))) + return; nr_lazy = atomic_long_add_return((va->va_end - va->va_start) >> PAGE_SHIFT, &vmap_lazy_nr); @@ -1871,6 +1870,19 @@ struct vmap_area *find_vmap_area(unsigned long addr) return va; } +static struct vmap_area *find_unlink_vmap_area(unsigned long addr) +{ + struct vmap_area *va; + + spin_lock(&vmap_area_lock); + va = __find_vmap_area(addr, &vmap_area_root); + if (va) + unlink_va(va, &vmap_area_root); + spin_unlock(&vmap_area_lock); + + return va; +} + /*** Per cpu kva allocator ***/ /* @@ -2015,6 +2027,10 @@ static void free_vmap_block(struct vmap_block *vb) tmp = xa_erase(&vmap_blocks, addr_to_vb_idx(vb->va->va_start)); BUG_ON(tmp != vb); + spin_lock(&vmap_area_lock); + unlink_va(vb->va, &vmap_area_root); + spin_unlock(&vmap_area_lock); + free_vmap_area_noflush(vb->va); kfree_rcu(vb, rcu_head); } @@ -2236,7 +2252,7 @@ void vm_unmap_ram(const void *mem, unsigned int count) return; } - va = find_vmap_area(addr); + va = find_unlink_vmap_area(addr); BUG_ON(!va); debug_check_no_locks_freed((void *)va->va_start, (va->va_end - va->va_start)); @@ -2591,6 +2607,20 @@ struct vm_struct *find_vm_area(const void *addr) return va->vm; } +static struct vm_struct *__remove_vm_area(struct vmap_area *va) +{ + struct vm_struct *vm; + + if (!va || !va->vm) + return NULL; + + vm = va->vm; + kasan_free_module_shadow(vm); + free_unmap_vmap_area(va); + + return vm; +} + /** * remove_vm_area - find and remove a continuous kernel virtual area * @addr: base address @@ -2603,26 +2633,10 @@ struct vm_struct *find_vm_area(const void *addr) */ struct vm_struct *remove_vm_area(const void *addr) { - struct vmap_area *va; - might_sleep(); - spin_lock(&vmap_area_lock); - va = __find_vmap_area((unsigned long)addr, &vmap_area_root); - if (va && va->vm) { - struct vm_struct *vm = va->vm; - - va->vm = NULL; - spin_unlock(&vmap_area_lock); - - kasan_free_module_shadow(vm); - free_unmap_vmap_area(va); - - return vm; - } - - spin_unlock(&vmap_area_lock); - return NULL; + return __remove_vm_area( + find_unlink_vmap_area((unsigned long) addr)); } static inline void set_area_direct_map(const struct vm_struct *area, @@ -2636,16 +2650,17 @@ static inline void set_area_direct_map(const struct vm_struct *area, set_direct_map(area->pages[i]); } -/* Handle removing and resetting vm mappings related to the vm_struct. */ -static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) +/* Handle removing and resetting vm mappings related to the VA's vm_struct. */ +static void va_remove_mappings(struct vmap_area *va, int deallocate_pages) { + struct vm_struct *area = va->vm; unsigned long start = ULONG_MAX, end = 0; unsigned int page_order = vm_area_page_order(area); int flush_reset = area->flags & VM_FLUSH_RESET_PERMS; int flush_dmap = 0; int i; - remove_vm_area(area->addr); + __remove_vm_area(va); /* If this is not VM_FLUSH_RESET_PERMS memory, no need for the below. */ if (!flush_reset) @@ -2690,6 +2705,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) static void __vunmap(const void *addr, int deallocate_pages) { struct vm_struct *area; + struct vmap_area *va; if (!addr) return; @@ -2698,19 +2714,20 @@ static void __vunmap(const void *addr, int deallocate_pages) addr)) return; - area = find_vm_area(addr); - if (unlikely(!area)) { + va = find_unlink_vmap_area((unsigned long)addr); + if (unlikely(!va)) { WARN(1, KERN_ERR "Trying to vfree() nonexistent vm area (%p)\n", addr); return; } + area = va->vm; debug_check_no_locks_freed(area->addr, get_vm_area_size(area)); debug_check_no_obj_freed(area->addr, get_vm_area_size(area)); kasan_poison_vmalloc(area->addr, get_vm_area_size(area)); - vm_remove_mappings(area, deallocate_pages); + va_remove_mappings(va, deallocate_pages); if (deallocate_pages) { int i; -- cgit