From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id B10876B02C3 for ; Tue, 18 Jul 2017 05:25:59 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id r74so1081788oie.1 for ; Tue, 18 Jul 2017 02:25:59 -0700 (PDT) Received: from sender-pp-092.zoho.com (sender-pp-092.zoho.com. [135.84.80.237]) by mx.google.com with ESMTPS id n130si1295680oih.7.2017.07.18.02.25.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Jul 2017 02:25:58 -0700 (PDT) Subject: Re: [PATCH v3] mm/vmalloc: terminate searching since one node found References: <1500366424-5882-1-git-send-email-zhaoyang.huang@spreadtrum.com> From: zijun_hu Message-ID: <596DD399.3030906@zoho.com> Date: Tue, 18 Jul 2017 17:23:37 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: =?UTF-8?B?Wmhhb3lhbmcgSHVhbmcgKOm7hOacnemYsyk=?= Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, zijun_hu@htc.com, Andrew Morton , Michal Hocko , Ingo Molnar , Vlastimil Babka , Thomas Garnier , "Kirill A. Shutemov" , Andrey Ryabinin linux-mm@kvack.orglinux-kernel@vger.kernel.org On 07/18/2017 04:31 PM, Zhaoyang Huang (>>AE3?No) wrote: > > It is no need to find the very beginning of the area within > alloc_vmap_area, which can be done by judging each node during the process > it seems the original code is wrote to achieve the following two purposes : A, the result vamp_area has the lowest available address in the required range [vstart, vend) B, it maybe update the cached vamp_area node info which can speedup other relative allocations it look redundant but conventional and necessary this approach maybe destroy the original purposes > For current approach, the worst case is that the starting node which be found > for searching the 'vmap_area_list' is close to the 'vstart', while the final > available one is round to the tail(especially for the left branch). > This commit have the list searching start at the first available node, which > will save the time of walking the rb tree'(1)' and walking the list'(2)'. > > vmap_area_root > / \ > tmp_next U > / > tmp > / > ... (1) > / > first(current approach) > @tmp_next is the next node of @tmp in the ordered list_head, not in the rbtree > vmap_area_list->...->first->...->tmp->tmp_next > (2) > > Signed-off-by: Zhaoyang Huang > --- > mm/vmalloc.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 34a1c3e..9a5c177 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -459,9 +459,18 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > > while (n) { > struct vmap_area *tmp; > + struct vmap_area *tmp_next; > tmp = rb_entry(n, struct vmap_area, rb_node); > + tmp_next = list_next_entry(tmp, list); > if (tmp->va_end >= addr) { > first = tmp; > + if (ALIGN(tmp->va_end, align) + size > + < tmp_next->va_start) { if @tmp node don't locate in the required rang [vstart, vend), but the right of the range it maybe satisfy this condition, even if it locate it locate within the range, it maybe don't have the lowest free address. if @tmp don't have the next node, tmp_next->va_start will cause NULL dereference > + addr = ALIGN(tmp->va_end, align); > + if (cached_hole_size >= size) > + cached_hole_size = 0; it seems a little rough to reset the @cached_hole_size by this way, it will caused the cached info is updated in the next allocation regardless the allocation arguments. > + goto found; > + } > if (tmp->va_start <= addr) > break; > n = n->rb_left; > -- > 1.9.1 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org