From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f52.google.com (mail-qg0-f52.google.com [209.85.192.52]) by kanga.kvack.org (Postfix) with ESMTP id D8A5D6B0038 for ; Wed, 7 Oct 2015 03:53:39 -0400 (EDT) Received: by qgev79 with SMTP id v79so8890460qge.0 for ; Wed, 07 Oct 2015 00:53:39 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id n68si33084374qhb.62.2015.10.07.00.53.39 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Oct 2015 00:53:39 -0700 (PDT) Date: Wed, 7 Oct 2015 00:58:20 -0700 From: Andrew Morton Subject: Re: [PATCH] memcg: convert threshold to bytes Message-Id: <20151007005820.54a0b2da.akpm@linux-foundation.org> In-Reply-To: <20151007073002.GA17444@dhcp22.suse.cz> References: <20151006170122.GB2752@dhcp22.suse.cz> <20151006122225.8a499b42f49d8484b61632a8@linux-foundation.org> <20151007073002.GA17444@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Shaohua Li , linux-mm@kvack.org, Johannes Weiner On Wed, 7 Oct 2015 09:30:02 +0200 Michal Hocko wrote: > On Tue 06-10-15 12:22:25, Andrew Morton wrote: > > On Tue, 6 Oct 2015 19:01:23 +0200 Michal Hocko wrote: > > > > > On Mon 05-10-15 14:44:22, Shaohua Li wrote: > > > > The page_counter_memparse() returns pages for the threshold, while > > > > mem_cgroup_usage() returns bytes for memory usage. Convert the threshold > > > > to bytes. > > > > > > > > Looks a regression introduced by 3e32cb2e0a12b69150 > > > > > > Yes. This suggests > > > Cc: stable # 3.19+ > > > > But it's been this way for 2 years and nobody noticed it. How come? > > Maybe we do not have that many users of this API with newer kernels. Either it's zero or all the users have worked around this bug. > > Or at least, nobody reported it. Maybe people *have* noticed it, and > > adjusted their userspace appropriately. In which case this patch will > > cause breakage. > > I dunno, I would rather have it fixed than keep bug to bug compatibility > because they would eventually move to a newer kernel one day when they > see the "breakage" anyway. They'd only see breakage if we fixed this in the newer kernel. We could just change the docs and leave it as-is. That it is called "usage_in_bytes" makes that a bit awkward. A bit of googling indicates that people are using usage_in_bytes. A few. All the discussions I found clearly predate this bug. So did people just stop using this? Is there some alternative way of getting the same info? Why does memcg_write_event_control() says "DO NOT USE IN NEW FILES" and "DO NOT ADD NEW FILES"? -- 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