Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752289AbcDOLIP (ORCPT ); Fri, 15 Apr 2016 07:08:15 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:33699 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752341AbcDOLHU (ORCPT ); Fri, 15 Apr 2016 07:07:20 -0400 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Cc: Chris Wilson , Joonas Lahtinen , Tvrtko Ursulin , Daniel Vetter , Andrew Morton , David Rientjes , Joonsoo Kim , Roman Pen , Mel Gorman , Toshi Kani , Shawn Lin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] mm/vmalloc: Keep a separate lazy-free list Date: Fri, 15 Apr 2016 12:07:06 +0100 Message-Id: <1460718426-20915-1-git-send-email-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.8.0.rc3 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4780 Lines: 144 When mixing lots of vmallocs and set_memory_*() (which calls vm_unmap_aliases()) I encountered situations where the performance degraded severely due to the walking of the entire vmap_area list each invocation. One simple improvement is to add the lazily freed vmap_area to a separate lockless free list, such that we then avoid having to walk the full list on each purge. v2: Remove unused VM_LAZY_FREE and VM_LAZY_FREEING flags and reorder access of vmap_area during addition to the lazy free list to avoid use-after free (Roman). Signed-off-by: Chris Wilson Cc: Joonas Lahtinen Cc: Tvrtko Ursulin Cc: Daniel Vetter Cc: Andrew Morton Cc: David Rientjes Cc: Joonsoo Kim Cc: Roman Pen Cc: Mel Gorman Cc: Toshi Kani Cc: Shawn Lin Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- include/linux/vmalloc.h | 3 ++- mm/vmalloc.c | 40 ++++++++++++++++++++-------------------- 2 files changed, 22 insertions(+), 21 deletions(-) diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 8b51df3ab334..3d9d786a943c 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -4,6 +4,7 @@ #include #include #include +#include #include /* pgprot_t */ #include @@ -45,7 +46,7 @@ struct vmap_area { unsigned long flags; struct rb_node rb_node; /* address sorted rbtree */ struct list_head list; /* address sorted list */ - struct list_head purge_list; /* "lazy purge" list */ + struct llist_node purge_list; /* "lazy purge" list */ struct vm_struct *vm; struct rcu_head rcu_head; }; diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 293889d7f482..70f942832164 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -275,13 +276,12 @@ EXPORT_SYMBOL(vmalloc_to_pfn); /*** Global kva allocator ***/ -#define VM_LAZY_FREE 0x01 -#define VM_LAZY_FREEING 0x02 #define VM_VM_AREA 0x04 static DEFINE_SPINLOCK(vmap_area_lock); /* Export for kexec only */ LIST_HEAD(vmap_area_list); +static LLIST_HEAD(vmap_purge_list); static struct rb_root vmap_area_root = RB_ROOT; /* The vmap cache globals are protected by vmap_area_lock */ @@ -628,7 +628,7 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end, int sync, int force_flush) { static DEFINE_SPINLOCK(purge_lock); - LIST_HEAD(valist); + struct llist_node *valist; struct vmap_area *va; struct vmap_area *n_va; int nr = 0; @@ -647,20 +647,14 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end, if (sync) purge_fragmented_blocks_allcpus(); - rcu_read_lock(); - list_for_each_entry_rcu(va, &vmap_area_list, list) { - if (va->flags & VM_LAZY_FREE) { - if (va->va_start < *start) - *start = va->va_start; - if (va->va_end > *end) - *end = va->va_end; - nr += (va->va_end - va->va_start) >> PAGE_SHIFT; - list_add_tail(&va->purge_list, &valist); - va->flags |= VM_LAZY_FREEING; - va->flags &= ~VM_LAZY_FREE; - } + valist = llist_del_all(&vmap_purge_list); + llist_for_each_entry(va, valist, purge_list) { + if (va->va_start < *start) + *start = va->va_start; + if (va->va_end > *end) + *end = va->va_end; + nr += (va->va_end - va->va_start) >> PAGE_SHIFT; } - rcu_read_unlock(); if (nr) atomic_sub(nr, &vmap_lazy_nr); @@ -670,7 +664,7 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end, if (nr) { spin_lock(&vmap_area_lock); - list_for_each_entry_safe(va, n_va, &valist, purge_list) + llist_for_each_entry_safe(va, n_va, valist, purge_list) __free_vmap_area(va); spin_unlock(&vmap_area_lock); } @@ -705,9 +699,15 @@ static void purge_vmap_area_lazy(void) */ static void free_vmap_area_noflush(struct vmap_area *va) { - va->flags |= VM_LAZY_FREE; - atomic_add((va->va_end - va->va_start) >> PAGE_SHIFT, &vmap_lazy_nr); - if (unlikely(atomic_read(&vmap_lazy_nr) > lazy_max_pages())) + int nr_lazy; + + nr_lazy = atomic_add_return((va->va_end - va->va_start) >> PAGE_SHIFT, + &vmap_lazy_nr); + + /* After this point, we may free va at any time */ + llist_add(&va->purge_list, &vmap_purge_list); + + if (unlikely(nr_lazy > lazy_max_pages())) try_purge_vmap_area_lazy(); } -- 2.8.0.rc3