From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C4C7C6FD18 for ; Tue, 28 Mar 2023 12:34:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B6FD66B0072; Tue, 28 Mar 2023 08:34:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B20076B0074; Tue, 28 Mar 2023 08:34:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9C0726B0075; Tue, 28 Mar 2023 08:34:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8C6566B0072 for ; Tue, 28 Mar 2023 08:34:22 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 60FA71A021E for ; Tue, 28 Mar 2023 12:34:22 +0000 (UTC) X-FDA: 80618249964.05.C2D0801 Received: from mail-lj1-f169.google.com (mail-lj1-f169.google.com [209.85.208.169]) by imf21.hostedemail.com (Postfix) with ESMTP id 3F10E1C0014 for ; Tue, 28 Mar 2023 12:34:19 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=UHjN4FGL; spf=pass (imf21.hostedemail.com: domain of urezki@gmail.com designates 209.85.208.169 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1680006860; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gvgN3DG+Vt2c71BXTWQsXRITKpPi7yyeQJ22Vh4BLvk=; b=54HtcWBQwG/bPHSb8WGwAzQWNTPSgyj7UvWxtsdZQsnFfw0wriSvJz31ksZuG4YUmqDjMa B6m1PGjUF7hjpfUkZdRgf9SBSnnfh/CD1Ey+NuQOAmfmX4C+YhtHozFDXvWMVJeHwH5p9i PkOA9y+WXusMEahQvbHU/xm4WhmKobw= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=UHjN4FGL; spf=pass (imf21.hostedemail.com: domain of urezki@gmail.com designates 209.85.208.169 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1680006860; a=rsa-sha256; cv=none; b=PP1P7KgFo+uoWPqfme/KJbl2KLzcyzZ1faXmPKIHl7NG5CuhhIvq9jZsVcQVJD1/IK+Umz X1hRh6ZZuSG8Wbi/LCmKHT3DHYPbEzkem5d1unMjJ313hR/yFuHmM3WgQWTHjBg413zkT+ EK0e7dma0CA83M9h9oURG1Cu4FlOep4= Received: by mail-lj1-f169.google.com with SMTP id e21so12369134ljn.7 for ; Tue, 28 Mar 2023 05:34:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1680006858; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=gvgN3DG+Vt2c71BXTWQsXRITKpPi7yyeQJ22Vh4BLvk=; b=UHjN4FGLf/NbvtVQ0GVXdo9eU/u1kFfW+B2fgTeJvWoFJaqA+6bRLY+YzILmv9bFRb c+C1u5SRZ5BUaNLyVtHiz3oGddTeYZiIVBJKRag1xvmZEYswRcjyRnQKVtOu34CZQelh QKK3oKkjh8Eup9tz1kiqPsRXdWc6PyXfBI3HN0x4hEFQcLFetlsdODkaW6nU/Qx17c5B EjjuwSJyn054SevEkv/hhQGBKmvRTgUuKA0dHtI4MXWQvMkx+CifEHfcY7aK2A7xLSFE xZgziLyaK8SUJxJMX0AlVQRHOj1qU/3TZdPR5IKL2BGrCi5SdCrtoKQcsD61pvuYKvYj nfNg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680006858; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gvgN3DG+Vt2c71BXTWQsXRITKpPi7yyeQJ22Vh4BLvk=; b=QYqg/+5KRpHgXy7jdw0gXQz0RvAz9afr71P6vsRY/tRoHI8iCBneKnoecfEP0D7Vpx odUCHYNRIIXwFxIsYhM1WIn87SxySD4kgWfj1pvz6UsVoTnnhMwC6TYqb27BQWwT5zba HSs0se3W+ugqIFtNUUNZmBG4TE3LZdaYCyUBy9DBUKnZGjbzQX+GReAsp4N4ajHjGHfY /8Hg2a9eboAa4VlIOo5H0nRFjR+wnMM6KhudRegvlPTKhg41mioNFd4RxDyWKgOvR7/E s3WiRHfRd7fnVX32V6yfkxrbYDDDF87Higj+cEf9fUhhcKuYEedVM7OeSILrdill7e1G uU1w== X-Gm-Message-State: AAQBX9eglnitSX65E2b/EQW0TpFO786RUZebZjLwUwJXRKalFW0BHjRZ jFHix5N5Nqn1B/44xUMGSaQ= X-Google-Smtp-Source: AKy350YH5LZkZudztmXURkXj9UQNwobEz57ljDoz1TGEBrGdnbpJiPkBajP68MeDDBE6mcL6ljrqaw== X-Received: by 2002:a05:651c:224:b0:295:c3cf:e81e with SMTP id z4-20020a05651c022400b00295c3cfe81emr4994443ljn.19.1680006858177; Tue, 28 Mar 2023 05:34:18 -0700 (PDT) Received: from pc636 (host-90-233-209-50.mobileonline.telia.com. [90.233.209.50]) by smtp.gmail.com with ESMTPSA id s13-20020a2e2c0d000000b0029a63256410sm4947064ljs.52.2023.03.28.05.34.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Mar 2023 05:34:17 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 28 Mar 2023 14:34:15 +0200 To: Baoquan He Cc: "Uladzislau Rezki (Sony)" , Andrew Morton , linux-mm@kvack.org, LKML , Lorenzo Stoakes , Christoph Hellwig , Matthew Wilcox , Dave Chinner , Oleksiy Avramchenko Subject: Re: [PATCH v3 1/2] mm: vmalloc: Remove a global vmap_blocks xarray Message-ID: References: <20230327170126.406044-1-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 3F10E1C0014 X-Stat-Signature: 73hodh57p1yf4uq7ifyq1g98md3aa8of X-Rspam-User: X-HE-Tag: 1680006859-695734 X-HE-Meta: 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 SmmOtlmp 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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: On Tue, Mar 28, 2023 at 11:25:54AM +0800, Baoquan He wrote: > On 03/27/23 at 07:01pm, Uladzislau Rezki (Sony) wrote: > > 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. > > With my understanding, the xarray will take more time when calling > xa_insert() or xa_erase() because these two will cause xa_expand() and > xa_shrink() if the index is sparse. xa_load() should be low cost to > finish. Wondering if in your testing code, the mapping address is close > or too far. > > 1 mm/vmalloc.c <> > err = xa_insert(&vmap_blocks, vb_idx, vb, gfp_mask); > 2 mm/vmalloc.c <> > tmp = xa_erase(&vmap_blocks, addr_to_vb_idx(vb->va->va_start)); > 3 mm/vmalloc.c <> > vb = xa_load(&vmap_blocks, addr_to_vb_idx(addr)); > 4 mm/vmalloc.c <> > vb = xa_load(&vmap_blocks, addr_to_vb_idx((unsigned long )addr)); > > > > > 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. > > > > v1 - v2: > > - Add more comments(Andrew Morton req.) > > - Switch to WARN_ON_ONCE(Lorenzo Stoakes req.) > > > > v2 -> v3: > > - Fix a kernel-doc complain(Matthew Wilcox) > > > > Signed-off-by: Uladzislau Rezki (Sony) > > --- > > mm/vmalloc.c | 85 +++++++++++++++++++++++++++++++++++++++------------- > > 1 file changed, 64 insertions(+), 21 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 978194dc2bb8..821256ecf81c 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1908,9 +1908,22 @@ static struct vmap_area *find_unlink_vmap_area(unsigned long addr) > > #define VMAP_BLOCK 0x2 /* mark out the vmap_block sub-type*/ > > #define VMAP_FLAGS_MASK 0x3 > > > > +/* > > + * 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. > > + */ > > struct vmap_block_queue { > > spinlock_t lock; > > struct list_head free; > > + > > + /* > > + * An xarray requires an extra memory dynamically to > > + * be allocated. If it is an issue, we can use rb-tree > > + * instead. > > + */ > > + struct xarray vmap_blocks; > > }; > > > > struct vmap_block { > > @@ -1928,24 +1941,46 @@ struct vmap_block { > > 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. > > + * In order to fast access to any "vmap_block" associated with a > > + * specific address, we store them into a per-cpu xarray. A hash > > + * function is addr_to_vbq() whereas a key is a vb->va->va_start > > + * value. > > + * > > + * Please note, a vmap_block_queue, which is a per-cpu, is not > > + * serialized by a raw_smp_processor_id() current CPU, instead > > + * it is chosen based on a CPU-index it belongs to, i.e. it is > > + * a hash-table. > > + * > > + * An example: > > + * > > + * CPU_1 CPU_2 CPU_0 > > + * | | | > > + * V V V > > + * 0 10 20 30 40 50 60 > > + * |------|------|------|------|------|------|... > > + * CPU0 CPU1 CPU2 CPU0 CPU1 CPU2 > > + * > > + * - CPU_1 invokes vm_unmap_ram(6), 6 belongs to CPU0 zone, thus > > + * it access: CPU0/INDEX0 -> vmap_blocks -> xa_lock; > > + * > > + * - CPU_2 invokes vm_unmap_ram(11), 11 belongs to CPU1 zone, thus > > + * it access: CPU1/INDEX1 -> vmap_blocks -> xa_lock; > > + * > > + * - CPU_0 invokes vm_unmap_ram(20), 20 belongs to CPU2 zone, thus > > + * it access: CPU2/INDEX2 -> vmap_blocks -> xa_lock. > > */ > > -static DEFINE_XARRAY(vmap_blocks); > > +static struct vmap_block_queue * > > +addr_to_vbq(unsigned long addr) > > +{ > > + int index = (addr / VMAP_BLOCK_SIZE) % num_possible_cpus(); > > > > -/* > > - * 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. > > - */ > > + return &per_cpu(vmap_block_queue, index); > > +} > > > > -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; > > + return rounddown(addr, VMAP_BLOCK_SIZE); > > } > > > > static void *vmap_block_vaddr(unsigned long va_start, unsigned long pages_off) > > @@ -1953,7 +1988,7 @@ 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)); > > + WARN_ON_ONCE(addr_to_vb_va_start(addr) != va_start); > > return (void *)addr; > > } > > > > @@ -1970,7 +2005,6 @@ 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 +2037,8 @@ 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); > > Using va->va_start as index to access xarray may cost extra memory. > Imagine we got a virtual address at VMALLOC_START, its region is > [VMALLOC_START, VMALLOC_START+4095]. In the xarray, its sequence order > is 0. While with va->va_start, it's 0xffffc90000000000UL on x86_64 with > level4 paging mode. That means for the first page size vmalloc area, > storing it into xarray need about 10 levels of xa_node, just for the one > page size. With the old addr_to_vb_idx(), its index is 0. Only one level > height is needed. One xa_node is about 72bytes, it could take more time > and memory to access va->va_start. Not sure if my understanding is correct. > > static unsigned long addr_to_vb_idx(unsigned long addr) > { > addr -= VMALLOC_START & ~(VMAP_BLOCK_SIZE-1); > addr /= VMAP_BLOCK_SIZE; > return addr; > } > If the size of array depends on index "length", then, indeed it will require more memory. From the other hand we can keep the old addr_to_vb_idx() function in order to "cut" a va->va_start index. -- Uladzislau Rezki