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Tue, 16 Jul 2019 08:58:37 -0700 (PDT) Received: from pc636 ([37.139.158.167]) by smtp.gmail.com with ESMTPSA id z12sm2922304lfg.67.2019.07.16.08.58.36 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 16 Jul 2019 08:58:36 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 16 Jul 2019 17:58:29 +0200 To: Pengfei Li Cc: akpm@linux-foundation.org, willy@infradead.org, urezki@gmail.com, rpenyaev@suse.de, peterz@infradead.org, guro@fb.com, rick.p.edgecombe@intel.com, rppt@linux.ibm.com, aryabinin@virtuozzo.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 2/2] mm/vmalloc: modify struct vmap_area to reduce its size Message-ID: <20190716155829.zdrzadrmwxrkfkro@pc636> References: <20190716152656.12255-1-lpf.vector@gmail.com> <20190716152656.12255-3-lpf.vector@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190716152656.12255-3-lpf.vector@gmail.com> User-Agent: NeoMutt/20170113 (1.7.2) 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, Jul 16, 2019 at 11:26:56PM +0800, Pengfei Li wrote: > Objective > --------- > The current implementation of struct vmap_area wasted space. > > After applying this commit, sizeof(struct vmap_area) has been > reduced from 11 words to 8 words. > > Description > ----------- > 1) Pack "subtree_max_size", "vm" and "purge_list". > This is no problem because > A) "subtree_max_size" is only used when vmap_area is in > "free" tree > B) "vm" is only used when vmap_area is in "busy" tree > C) "purge_list" is only used when vmap_area is in > vmap_purge_list > > 2) Eliminate "flags". > Since only one flag VM_VM_AREA is being used, and the same > thing can be done by judging whether "vm" is NULL, then the > "flags" can be eliminated. > > Signed-off-by: Pengfei Li > Suggested-by: Uladzislau Rezki (Sony) > --- > include/linux/vmalloc.h | 20 +++++++++++++------- > mm/vmalloc.c | 24 ++++++++++-------------- > 2 files changed, 23 insertions(+), 21 deletions(-) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index 9b21d0047710..a1334bd18ef1 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -51,15 +51,21 @@ struct vmap_area { > unsigned long va_start; > unsigned long va_end; > > - /* > - * Largest available free size in subtree. > - */ > - unsigned long subtree_max_size; > - unsigned long flags; > struct rb_node rb_node; /* address sorted rbtree */ > struct list_head list; /* address sorted list */ > - struct llist_node purge_list; /* "lazy purge" list */ > - struct vm_struct *vm; > + > + /* > + * The following three variables can be packed, because > + * a vmap_area object is always one of the three states: > + * 1) in "free" tree (root is vmap_area_root) > + * 2) in "busy" tree (root is free_vmap_area_root) > + * 3) in purge list (head is vmap_purge_list) > + */ > + union { > + unsigned long subtree_max_size; /* in "free" tree */ > + struct vm_struct *vm; /* in "busy" tree */ > + struct llist_node purge_list; /* in purge list */ > + }; > }; > > /* > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 71d8040a8a0b..2f7edc0466e7 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -329,7 +329,6 @@ EXPORT_SYMBOL(vmalloc_to_pfn); > #define DEBUG_AUGMENT_PROPAGATE_CHECK 0 > #define DEBUG_AUGMENT_LOWEST_MATCH_CHECK 0 > > -#define VM_VM_AREA 0x04 > > static DEFINE_SPINLOCK(vmap_area_lock); > /* Export for kexec only */ > @@ -1115,7 +1114,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > > va->va_start = addr; > va->va_end = addr + size; > - va->flags = 0; > + va->vm = NULL; > insert_vmap_area(va, &vmap_area_root, &vmap_area_list); > > spin_unlock(&vmap_area_lock); > @@ -1922,7 +1921,6 @@ void __init vmalloc_init(void) > if (WARN_ON_ONCE(!va)) > continue; > > - va->flags = VM_VM_AREA; > va->va_start = (unsigned long)tmp->addr; > va->va_end = va->va_start + tmp->size; > va->vm = tmp; > @@ -2020,7 +2018,6 @@ static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va, > vm->size = va->va_end - va->va_start; > vm->caller = caller; > va->vm = vm; > - va->flags |= VM_VM_AREA; > spin_unlock(&vmap_area_lock); > } > > @@ -2125,10 +2122,10 @@ struct vm_struct *find_vm_area(const void *addr) > struct vmap_area *va; > > va = find_vmap_area((unsigned long)addr); > - if (va && va->flags & VM_VM_AREA) > - return va->vm; > + if (!va) > + return NULL; > > - return NULL; > + return va->vm; > } > > /** > @@ -2149,11 +2146,10 @@ struct vm_struct *remove_vm_area(const void *addr) > > spin_lock(&vmap_area_lock); > va = __find_vmap_area((unsigned long)addr); > - if (va && va->flags & VM_VM_AREA) { > + if (va && va->vm) { > struct vm_struct *vm = va->vm; > > va->vm = NULL; > - va->flags &= ~VM_VM_AREA; > spin_unlock(&vmap_area_lock); > > kasan_free_shadow(vm); > @@ -2856,7 +2852,7 @@ long vread(char *buf, char *addr, unsigned long count) > if (!count) > break; > > - if (!(va->flags & VM_VM_AREA)) > + if (!va->vm) > continue; > > vm = va->vm; > @@ -2936,7 +2932,7 @@ long vwrite(char *buf, char *addr, unsigned long count) > if (!count) > break; > > - if (!(va->flags & VM_VM_AREA)) > + if (!va->vm) > continue; > > vm = va->vm; > @@ -3466,10 +3462,10 @@ static int s_show(struct seq_file *m, void *p) > va = list_entry(p, struct vmap_area, list); > > /* > - * s_show can encounter race with remove_vm_area, !VM_VM_AREA on > - * behalf of vmap area is being tear down or vm_map_ram allocation. > + * s_show can encounter race with remove_vm_area, !vm on behalf > + * of vmap area is being tear down or vm_map_ram allocation. > */ > - if (!(va->flags & VM_VM_AREA)) { > + if (!va->vm) { > seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n", > (void *)va->va_start, (void *)va->va_end, > va->va_end - va->va_start); > -- > 2.21.0 > This patch depends on https://lkml.org/lkml/2019/7/16/276 and looks ok to me, so Reviewed-by: Uladzislau Rezki (Sony) Thanks! -- Vlad Rezki