From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id A27DB6B0006 for ; Mon, 30 Jul 2018 04:53:56 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id l4-v6so7489804wme.7 for ; Mon, 30 Jul 2018 01:53:56 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o5-v6si891960wre.145.2018.07.30.01.53.54 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 30 Jul 2018 01:53:55 -0700 (PDT) Subject: Re: [PATCH 4/4] mm: proc/pid/smaps_rollup: convert to single value seq_file References: <20180723111933.15443-1-vbabka@suse.cz> <20180723111933.15443-5-vbabka@suse.cz> <20180726162637.GB25227@avx2> From: Vlastimil Babka Message-ID: Date: Mon, 30 Jul 2018 10:53:53 +0200 MIME-Version: 1.0 In-Reply-To: <20180726162637.GB25227@avx2> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Alexey Dobriyan Cc: Andrew Morton , Daniel Colascione , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org On 07/26/2018 06:26 PM, Alexey Dobriyan wrote: > On Wed, Jul 25, 2018 at 08:53:53AM +0200, Vlastimil Babka wrote: >> I moved the reply to this thread since the "added to -mm tree" >> notification Alexey replied to in <20180724182908.GD27053@avx2> has >> reduced CC list and is not linked to the patch postings. >> >> On 07/24/2018 08:29 PM, Alexey Dobriyan wrote: >>> On Mon, Jul 23, 2018 at 04:55:48PM -0700, akpm@linux-foundation.org wrote: >>>> The patch titled >>>> Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file >>>> has been added to the -mm tree. Its filename is >>>> mm-proc-pid-smaps_rollup-convert-to-single-value-seq_file.patch >>> >>>> Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file >>>> >>>> The /proc/pid/smaps_rollup file is currently implemented via the >>>> m_start/m_next/m_stop seq_file iterators shared with the other maps files, >>>> that iterate over vma's. However, the rollup file doesn't print anything >>>> for each vma, only accumulate the stats. >>> >>> What I don't understand why keep seq_ops then and not do all the work in >>> ->show hook. Currently /proc/*/smaps_rollup is at ~500 bytes so with >>> minimum 1 page seq buffer, no buffer resizing is possible. >> >> Hmm IIUC seq_file also provides the buffer and handles feeding the data >> from there to the user process, which might have called read() with a smaller >> buffer than that. So I would rather not avoid the seq_file infrastructure. >> Or you're saying it could be converted to single_open()? Maybe, with more work. > > Prefereably yes. OK here it is. Sending as a new patch instead of delta, as that's easier to review - the delta is significant. Line stats wise it's the same. Again a bit less boilerplate thans to no special seq_ops, a bit more copy/paste in the open and release functions. But I guess it's better overall. ----8>----