From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id 7D93F6B0069 for ; Fri, 19 Aug 2016 13:43:19 -0400 (EDT) Received: by mail-io0-f198.google.com with SMTP id q83so147829750iod.0 for ; Fri, 19 Aug 2016 10:43:19 -0700 (PDT) Received: from smtprelay.hostedemail.com (smtprelay0157.hostedemail.com. [216.40.44.157]) by mx.google.com with ESMTPS id n70si5826035ith.121.2016.08.19.10.43.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 19 Aug 2016 10:43:18 -0700 (PDT) Message-ID: <1471628595.3893.23.camel@perches.com> Subject: Re: [PATCH 0/2] fs, proc: optimize smaps output formatting From: Joe Perches Date: Fri, 19 Aug 2016 10:43:15 -0700 In-Reply-To: <1471601580-17999-1-git-send-email-mhocko@kernel.org> References: <1471519888-13829-1-git-send-email-mhocko@kernel.org> <1471601580-17999-1-git-send-email-mhocko@kernel.org> Content-Type: text/plain; charset="ISO-8859-1" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Andrew Morton Cc: Jann Horn , linux-mm@kvack.org, LKML On Fri, 2016-08-19 at 12:12 +0200, Michal Hocko wrote: > Hi, > this is rebased on top of next-20160818. Joe has pointed out that > meminfo is using a similar trick so I have extracted guts of what we > have already and made it more generic to be usable for smaps as well > (patch 1). The second patch then replaces seq_printf with seq_write > and show_val_kb which should have smaller overhead and my measuring (in > kvm) shows quite a nice improvements. I hope kvm is not playing tricks > on me but I didn't get to test on a real HW. Hi Michal. A few comments: For the first patch: I think this isn't worth the expansion in object size (x86-64 defconfig) $ size fs/proc/meminfo.o* text data bss dec hex filename 2698 8 0 2706 a92 fs/proc/meminfo.o.new 2142 8 0 2150 866 fs/proc/meminfo.o.old Creating a new static in task_mmu would be smaller and faster code. There are only 3 other uses of %8lu in fs/proc/task_nommu.c and those use bytes not kB. There are a few other likely not performance sensitive similar uses in /mm $ git grep -E "seq_printf.*%8lu kB" arch arch/x86/mm/pageattr.c: seq_printf(m, "DirectMap4k: %8lu kB\n", arch/x86/mm/pageattr.c: seq_printf(m, "DirectMap2M: %8lu kB\n", arch/x86/mm/pageattr.c: seq_printf(m, "DirectMap4M: %8lu kB\n", arch/x86/mm/pageattr.c: seq_printf(m, "DirectMap1G: %8lu kB\n", arch/s390/mm/pageattr.c: seq_printf(m, "DirectMap4k: %8lu kB\n", arch/s390/mm/pageattr.c: seq_printf(m, "DirectMap1M: %8lu kB\n", arch/s390/mm/pageattr.c: seq_printf(m, "DirectMap2G: %8lu kB\n", For the second patch: seq_show starts with a PAGE_SIZE buffer and if that buffer isn't big enough, seq_show redoes the entire output done to that point into a new buffer << 1 until the buffer is big enough to hold the output. So I expect this case of multiple pages / megabytes worth of smap output (40MB in your pathological case) would be rather faster if single_open_size was used appropriately for expected output size. And this would definitely be faster if seq_has_overflowed() was used somewhere in the iteration loop. -- 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