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[209.85.220.65]) by mx.google.com with SMTPS id r136sor4442608oie.105.2019.07.12.08.09.12 for (Google Transport Security); Fri, 12 Jul 2019 08:09:12 -0700 (PDT) Received-SPF: pass (google.com: domain of lpf.vector@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=i30lgvwL; spf=pass (google.com: domain of lpf.vector@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=lpf.vector@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=MJ8/wMSygZBfB3wNzWuYzcvp2/BWwETDvXU2IK3PdxQ=; b=i30lgvwLkeVpXQsVjPYonpEPiGWlUBv2z2qDgJQMxrpKENxTorJSehxeqy+LUhfYzv VtQK7axqN3W8U1LkXDuWZF1uP/L2p5KuLxKw4qI6wW++8B5fsIOnjjNBcW6teOiQ7tII mzaCC2ZUY+uYaRDsXXA4s9KcaDlBUAOOWLZdYfvJUEAQEBDrP1cVZ7aiVZqE4JPjLspM gGX5Sxlw25a4BwETR5XcKtZkSZrIlIkMg/I5T2vbeOKWQ6GxTtCPuP3CCKEjJvhuAnNI gUc8VfcZTZNpYUjORWUUYKbazILP48oH1baF5oAlWmAp2Iq73gk63PjeR6tPL6TgX/5n EdVg== X-Google-Smtp-Source: APXvYqx6mGiQZVnuJ8vBdqFSeKXfLAml4k5LUaP7pbQDRWmiFpLAtMv5q6hcSKqWv8vY99TgvNNCYqHMtYCIHspx+74= X-Received: by 2002:a05:6808:4d:: with SMTP id v13mr6048794oic.22.1562944151822; Fri, 12 Jul 2019 08:09:11 -0700 (PDT) MIME-Version: 1.0 References: <20190712120213.2825-1-lpf.vector@gmail.com> <20190712120213.2825-3-lpf.vector@gmail.com> <20190712134955.GV32320@bombadil.infradead.org> In-Reply-To: <20190712134955.GV32320@bombadil.infradead.org> From: Pengfei Li Date: Fri, 12 Jul 2019 23:09:00 +0800 Message-ID: Subject: Re: [PATCH v4 2/2] mm/vmalloc.c: Modify struct vmap_area to reduce its size To: Matthew Wilcox Cc: Andrew Morton , Uladzislau Rezki , 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 Content-Type: text/plain; charset="UTF-8" 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 Fri, Jul 12, 2019 at 9:49 PM Matthew Wilcox wrote: > > On Fri, Jul 12, 2019 at 08:02:13PM +0800, Pengfei Li wrote: > > I don't think you need struct union struct union. Because llist_node > is just a pointer, you can get the same savings with just: > > union { > struct llist_node purge_list; > struct vm_struct *vm; > unsigned long subtree_max_size; > }; > Thanks for your comments. As you said, I did this in v3. https://patchwork.kernel.org/patch/11031507/ The reason why I use struct union struct in v4 is that I want to express "in the tree" and "in the purge list" are two completely isolated cases. struct vmap_area { union { struct { /* Case A: In the tree */ ... }; struct { /* Case B: In the purge list */ ... }; }; }; The "rb_node" and "list" should also not be used when va is in the purge list what do you think of this idea?