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Thu, 23 Mar 2023 12:21:14 -0700 (PDT) Received: from pc638.lan ([155.137.26.201]) by smtp.gmail.com with ESMTPSA id lz24-20020a170906fb1800b009334309eda5sm7213127ejb.196.2023.03.23.12.21.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Mar 2023 12:21:14 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: Andrew Morton Cc: linux-mm@kvack.org, LKML , Baoquan He , Lorenzo Stoakes , Christoph Hellwig , Matthew Wilcox , Dave Chinner , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH 1/1] mm: vmalloc: Remove a global vmap_blocks xarray Date: Thu, 23 Mar 2023 20:21:11 +0100 Message-Id: <20230323192111.1501308-1-urezki@gmail.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 9F2341C0006 X-Stat-Signature: f8tmz3edjt8br9ciucp597n3ch1confx X-HE-Tag: 1679599276-951052 X-HE-Meta: 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 Q53XcUFx 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: A global vmap_blocks-xarray array can be contented under heavy usage of the vm_map_ram()/vm_unmap_ram() APIs. The lock_stat shows that a "vmap_blocks.xa_lock" lock is a second in a top-list when it comes to contentions: ---------------------------------------- class name con-bounces contentions ... ---------------------------------------- vmap_area_lock: 2554079 2554276 ... -------------- vmap_area_lock 1297948 [<00000000dd41cbaa>] alloc_vmap_area+0x1c7/0x910 vmap_area_lock 1256330 [<000000009d927bf3>] free_vmap_block+0x4a/0xe0 vmap_area_lock 1 [<00000000c95c05a7>] find_vm_area+0x16/0x70 -------------- vmap_area_lock 1738590 [<00000000dd41cbaa>] alloc_vmap_area+0x1c7/0x910 vmap_area_lock 815688 [<000000009d927bf3>] free_vmap_block+0x4a/0xe0 vmap_area_lock 1 [<00000000c1d619d7>] __get_vm_area_node+0xd2/0x170 vmap_blocks.xa_lock: 862689 862698 ... ------------------- vmap_blocks.xa_lock 378418 [<00000000625a5626>] vm_map_ram+0x359/0x4a0 vmap_blocks.xa_lock 484280 [<00000000caa2ef03>] xa_erase+0xe/0x30 ------------------- vmap_blocks.xa_lock 576226 [<00000000caa2ef03>] xa_erase+0xe/0x30 vmap_blocks.xa_lock 286472 [<00000000625a5626>] vm_map_ram+0x359/0x4a0 ... that is a result of running vm_map_ram()/vm_unmap_ram() in a loop. The test creates 64(on 64 CPUs system) threads and each one maps/unmaps 1 page. After this change the "xa_lock" can be considered as a noise in the same test condition: ... &xa->xa_lock#1: 10333 10394 ... -------------- &xa->xa_lock#1 5349 [<00000000bbbc9751>] xa_erase+0xe/0x30 &xa->xa_lock#1 5045 [<0000000018def45d>] vm_map_ram+0x3a4/0x4f0 -------------- &xa->xa_lock#1 7326 [<0000000018def45d>] vm_map_ram+0x3a4/0x4f0 &xa->xa_lock#1 3068 [<00000000bbbc9751>] xa_erase+0xe/0x30 ... This patch does not fix vmap_area_lock/free_vmap_area_lock and purge_vmap_area_lock bottle-necks, it is rather a separate rework. Signed-off-by: Uladzislau Rezki (Sony) --- mm/vmalloc.c | 50 ++++++++++++++++++++++++++------------------------ 1 file changed, 26 insertions(+), 24 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 978194dc2bb8..13b5342bed9a 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1911,6 +1911,7 @@ static struct vmap_area *find_unlink_vmap_area(unsigned long addr) struct vmap_block_queue { spinlock_t lock; struct list_head free; + struct xarray vmap_blocks; }; struct vmap_block { @@ -1927,25 +1928,18 @@ struct vmap_block { /* Queue of free and dirty vmap blocks, for allocation and flushing purposes */ static DEFINE_PER_CPU(struct vmap_block_queue, vmap_block_queue); -/* - * XArray of vmap blocks, indexed by address, to quickly find a vmap block - * in the free path. Could get rid of this if we change the API to return a - * "cookie" from alloc, to be passed to free. But no big deal yet. - */ -static DEFINE_XARRAY(vmap_blocks); - -/* - * We should probably have a fallback mechanism to allocate virtual memory - * out of partially filled vmap blocks. However vmap block sizing should be - * fairly reasonable according to the vmalloc size, so it shouldn't be a - * big problem. - */ +static struct vmap_block_queue * +addr_to_vbq(unsigned long addr) +{ + int cpu = (addr / VMAP_BLOCK_SIZE) % num_possible_cpus(); + return &per_cpu(vmap_block_queue, cpu); +} -static unsigned long addr_to_vb_idx(unsigned long addr) +static unsigned long +addr_to_vb_va_start(unsigned long addr) { - addr -= VMALLOC_START & ~(VMAP_BLOCK_SIZE-1); - addr /= VMAP_BLOCK_SIZE; - return addr; + /* A start address of block an address belongs to. */ + return rounddown(addr, VMAP_BLOCK_SIZE); } static void *vmap_block_vaddr(unsigned long va_start, unsigned long pages_off) @@ -1953,7 +1947,7 @@ static void *vmap_block_vaddr(unsigned long va_start, unsigned long pages_off) unsigned long addr; addr = va_start + (pages_off << PAGE_SHIFT); - BUG_ON(addr_to_vb_idx(addr) != addr_to_vb_idx(va_start)); + BUG_ON(addr_to_vb_va_start(addr) != addr_to_vb_va_start(va_start)); return (void *)addr; } @@ -1970,7 +1964,6 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask) struct vmap_block_queue *vbq; struct vmap_block *vb; struct vmap_area *va; - unsigned long vb_idx; int node, err; void *vaddr; @@ -2003,8 +1996,8 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask) bitmap_set(vb->used_map, 0, (1UL << order)); INIT_LIST_HEAD(&vb->free_list); - vb_idx = addr_to_vb_idx(va->va_start); - err = xa_insert(&vmap_blocks, vb_idx, vb, gfp_mask); + vbq = addr_to_vbq(va->va_start); + err = xa_insert(&vbq->vmap_blocks, va->va_start, vb, gfp_mask); if (err) { kfree(vb); free_vmap_area(va); @@ -2021,9 +2014,11 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask) static void free_vmap_block(struct vmap_block *vb) { + struct vmap_block_queue *vbq; struct vmap_block *tmp; - tmp = xa_erase(&vmap_blocks, addr_to_vb_idx(vb->va->va_start)); + vbq = addr_to_vbq(vb->va->va_start); + tmp = xa_erase(&vbq->vmap_blocks, vb->va->va_start); BUG_ON(tmp != vb); spin_lock(&vmap_area_lock); @@ -2135,6 +2130,7 @@ static void vb_free(unsigned long addr, unsigned long size) unsigned long offset; unsigned int order; struct vmap_block *vb; + struct vmap_block_queue *vbq; BUG_ON(offset_in_page(size)); BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC); @@ -2143,7 +2139,10 @@ static void vb_free(unsigned long addr, unsigned long size) order = get_order(size); offset = (addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT; - vb = xa_load(&vmap_blocks, addr_to_vb_idx(addr)); + + vbq = addr_to_vbq(addr); + vb = xa_load(&vbq->vmap_blocks, addr_to_vb_va_start(addr)); + spin_lock(&vb->lock); bitmap_clear(vb->used_map, offset, (1UL << order)); spin_unlock(&vb->lock); @@ -3486,6 +3485,7 @@ static void vmap_ram_vread(char *buf, char *addr, int count, unsigned long flags { char *start; struct vmap_block *vb; + struct vmap_block_queue *vbq; unsigned long offset; unsigned int rs, re, n; @@ -3503,7 +3503,8 @@ static void vmap_ram_vread(char *buf, char *addr, int count, unsigned long flags * Area is split into regions and tracked with vmap_block, read out * each region and zero fill the hole between regions. */ - vb = xa_load(&vmap_blocks, addr_to_vb_idx((unsigned long)addr)); + vbq = addr_to_vbq((unsigned long) addr); + vb = xa_load(&vbq->vmap_blocks, addr_to_vb_va_start((unsigned long) addr)); if (!vb) goto finished; @@ -4272,6 +4273,7 @@ void __init vmalloc_init(void) p = &per_cpu(vfree_deferred, i); init_llist_head(&p->list); INIT_WORK(&p->wq, delayed_vfree_work); + xa_init(&vbq->vmap_blocks); } /* Import existing vmlist entries. */