From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f72.google.com (mail-lf0-f72.google.com [209.85.215.72]) by kanga.kvack.org (Postfix) with ESMTP id C801B6B0069 for ; Mon, 22 Aug 2016 03:24:17 -0400 (EDT) Received: by mail-lf0-f72.google.com with SMTP id 33so68048281lfw.1 for ; Mon, 22 Aug 2016 00:24:17 -0700 (PDT) Received: from mail-wm0-f66.google.com (mail-wm0-f66.google.com. [74.125.82.66]) by mx.google.com with ESMTPS id u138si14986834wmu.42.2016.08.22.00.24.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Aug 2016 00:24:16 -0700 (PDT) Received: by mail-wm0-f66.google.com with SMTP id o80so12102897wme.0 for ; Mon, 22 Aug 2016 00:24:16 -0700 (PDT) Date: Mon, 22 Aug 2016 09:24:15 +0200 From: Michal Hocko Subject: Re: [PATCH 2/2] proc: task_mmu: Reduce output processing cpu time Message-ID: <20160822072414.GB13596@dhcp22.suse.cz> References: <2c1ea0d8f35fa5ddea477369b273d6d91c5bf2e2.1471679737.git.joe@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2c1ea0d8f35fa5ddea477369b273d6d91c5bf2e2.1471679737.git.joe@perches.com> Sender: owner-linux-mm@kvack.org List-ID: To: Joe Perches Cc: linux-kernel@vger.kernel.org, Andrew Morton , Jann Horn , linux-mm@kvack.org On Sat 20-08-16 01:00:17, Joe Perches wrote: [...] > static int proc_maps_open(struct inode *inode, struct file *file, > const struct seq_operations *ops, int psize) > { > - struct proc_maps_private *priv = __seq_open_private(file, ops, psize); > + struct proc_maps_private *priv; > + struct mm_struct *mm; > + > + mm = proc_mem_open(inode, PTRACE_MODE_READ); > + if (IS_ERR(mm)) > + return PTR_ERR(mm); > > + priv = __seq_open_private_bufsize(file, ops, psize, > + mm && mm->map_count ? > + mm->map_count * 0x300 : PAGE_SIZE); NAK to this! Seriously, this just gives any random user access to user defined amount of memory which not accounted, not reclaimable and a potential consumer of any higher order blocks. Besides that, at least one show_smap output will always fit inside the single page and AFAIR (it's been quite a while since I've looked into seq_file internals) the buffer grows only when the single show doesn't fit in. > if (!priv) > return -ENOMEM; > > priv->inode = inode; > - priv->mm = proc_mem_open(inode, PTRACE_MODE_READ); > - if (IS_ERR(priv->mm)) { > - int err = PTR_ERR(priv->mm); > - > - seq_release_private(inode, file); > - return err; > - } > + priv->mm = mm; > > return 0; > } > @@ -721,6 +723,25 @@ void __weak arch_show_smap(struct seq_file *m, struct vm_area_struct *vma) > { > } > > +static void show_val_kb(struct seq_file *m, const char *s, unsigned long num) > +{ > + char v[32]; > + static const char blanks[7] = {' ', ' ', ' ', ' ',' ', ' ', ' '}; > + int len; > + > + len = num_to_str(v, sizeof(v), num >> 10); > + > + seq_write(m, s, 16); > + > + if (len > 0) { > + if (len < 8) > + seq_write(m, blanks, 8 - len); > + > + seq_write(m, v, len); > + } > + seq_write(m, " kB\n", 4); > +} > + I really do not understand why you insist on code duplication rather than reuse but if you really insist then just make this (without the above __seq_open_private_bufsize, re-measure and add the results to the changelog and repost. -- Michal Hocko SUSE Labs -- 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