From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8A09C33CAF for ; Thu, 16 Jan 2020 22:44:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F65B20748 for ; Thu, 16 Jan 2020 22:44:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Hb3TDPh8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387638AbgAPWo7 (ORCPT ); Thu, 16 Jan 2020 17:44:59 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:43012 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732417AbgAPWo6 (ORCPT ); Thu, 16 Jan 2020 17:44:58 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00GMcQbe059559; Thu, 16 Jan 2020 22:44:50 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2019-08-05; bh=jlzdnATHqqaoRnZjE+SFSnSnRkAzXmaHY4RqPn2GR14=; b=Hb3TDPh83eiTfrX6Rmpx/FtUaekfBHuaXEkqSQU3gyu4w+ATUwFA9Z6N8AdSNh/mfyJ/ XKSNvGJ6mOHHCrwI9Dq0fHCsLbg6Z/guPvZlAqt+Q+1p6BY8Wz7cGuDiAr9kmmG19tss kDzNdcWehvTlQ53be0RNk1ZxEYvVo03BQeCQ7dAnA+JEGfMxSv+PAffV1eQTcbZ8ADSQ hbET9KgS1x/+fDtnS+JxuXAlcEVwgp3UvQv/B7JMW7l8ItY+FJDHzdleu3E57tozfGGE hYDS+uA3y6Y20pq/21gAeMm477K7JJkwgEGgQnZqJTxANQjOda6Rq3dLaSugaf+c0qDa gA== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by userp2120.oracle.com with ESMTP id 2xf73ywhy2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Jan 2020 22:44:49 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00GMdQt8015176; Thu, 16 Jan 2020 22:44:48 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3030.oracle.com with ESMTP id 2xj61nc4gv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Jan 2020 22:44:48 +0000 Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 00GMili4017672; Thu, 16 Jan 2020 22:44:47 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 16 Jan 2020 14:44:47 -0800 Subject: Re: [PATCH v10 1/8] hugetlb_cgroup: Add hugetlb_cgroup reservation counter To: Mina Almasry , rientjes@google.com, shakeelb@google.com Cc: shuah@kernel.org, gthelen@google.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com References: <20200115012651.228058-1-almasrymina@google.com> From: Mike Kravetz Message-ID: Date: Thu, 16 Jan 2020 14:44:45 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200115012651.228058-1-almasrymina@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9502 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001160181 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9502 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001160181 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 1/14/20 5:26 PM, Mina Almasry wrote: > These counters will track hugetlb reservations rather than hugetlb > memory faulted in. This patch only adds the counter, following patches > add the charging and uncharging of the counter. > > This is patch 1 of an 8 patch series. > > Problem: > Currently tasks attempting to reserve more hugetlb memory than is available get > a failure at mmap/shmget time. This is thanks to Hugetlbfs Reservations [1]. > However, if a task attempts to reserve hugetlb memory only more than its *reword* However, if a task attempts to reserve more hugetlb memory than its > hugetlb_cgroup limit allows, the kernel will allow the mmap/shmget call, > but will SIGBUS the task when it attempts to fault the memory in. *reword* but will SIGBUS the task when it attempts to fault in the excess memory. > > We have users hitting their hugetlb_cgroup limits and thus we've been > looking at this failure mode. We'd like to improve this behavior such that users > violating the hugetlb_cgroup limits get an error on mmap/shmget time, rather > than getting SIGBUS'd when they try to fault the excess memory in. This > gives the user an opportunity to fallback more gracefully to > non-hugetlbfs memory for example. > > The underlying problem is that today's hugetlb_cgroup accounting happens > at hugetlb memory *fault* time, rather than at *reservation* time. > Thus, enforcing the hugetlb_cgroup limit only happens at fault time, and > the offending task gets SIGBUS'd. > > Proposed Solution: > A new page counter named > 'hugetlb.xMB.reservation_[limit|usage|max_usage]_in_bytes'. This counter has > slightly different semantics than You changed the name to 'hugetlb.xMB.resv_[limit|usage|max_usage]_in_bytes' in the code, but left this description. Also, David suggested 'rsvd' as the abbreviation to use here. I would also prefer that name to be consistent with other hugetlb interfaces. > 'hugetlb.xMB.[limit|usage|max_usage]_in_bytes': > > - While usage_in_bytes tracks all *faulted* hugetlb memory, > reservation_usage_in_bytes tracks all *reserved* hugetlb memory and > hugetlb memory faulted in without a prior reservation. > > - If a task attempts to reserve more memory than limit_in_bytes allows, > the kernel will allow it to do so. But if a task attempts to reserve > more memory than reservation_limit_in_bytes, the kernel will fail this > reservation. > > This proposal is implemented in this patch series, with tests to verify > functionality and show the usage. > > Alternatives considered: > 1. A new cgroup, instead of only a new page_counter attached to > the existing hugetlb_cgroup. Adding a new cgroup seemed like a lot of code > duplication with hugetlb_cgroup. Keeping hugetlb related page counters under > hugetlb_cgroup seemed cleaner as well. > > 2. Instead of adding a new counter, we considered adding a sysctl that modifies > the behavior of hugetlb.xMB.[limit|usage]_in_bytes, to do accounting at > reservation time rather than fault time. Adding a new page_counter seems > better as userspace could, if it wants, choose to enforce different cgroups > differently: one via limit_in_bytes, and another via > reservation_limit_in_bytes. This could be very useful if you're > transitioning how hugetlb memory is partitioned on your system one > cgroup at a time, for example. Also, someone may find usage for both > limit_in_bytes and reservation_limit_in_bytes concurrently, and this > approach gives them the option to do so. > > Testing: > - Added tests passing. > - Used libhugetlbfs for regression testing. > > [1]: https://www.kernel.org/doc/html/latest/vm/hugetlbfs_reserv.html > > Signed-off-by: Mina Almasry > > --- > Changes in v10: > - Renamed reservation_* to resv.* > > --- > include/linux/hugetlb.h | 4 +- > mm/hugetlb_cgroup.c | 115 +++++++++++++++++++++++++++++++++++----- > 2 files changed, 104 insertions(+), 15 deletions(-) The code looks fine to me. With the commit message and naming updates, I will add a Reviewed-by: Please do wait a few/several days before sending a revised edition to make sure we get all feedback. I really would like to get comments from people more familiar with cgroups. -- Mike Kravetz