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 9CC99C33CA9 for ; Mon, 13 Jan 2020 18:44:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 698D921569 for ; Mon, 13 Jan 2020 18:44:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="TEFnciVL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728831AbgAMSoS (ORCPT ); Mon, 13 Jan 2020 13:44:18 -0500 Received: from userp2130.oracle.com ([156.151.31.86]:58918 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728664AbgAMSoS (ORCPT ); Mon, 13 Jan 2020 13:44:18 -0500 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00DIhSuM014798; Mon, 13 Jan 2020 18:44:05 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=58bZpuiFAks0nyTSTapJdzHryQVmx7OwYqtXIuvSXB4=; b=TEFnciVLOWX1iv14uTDL8MJpviCcdFoR7s5SF/pkyIHJbsjDrBA43BxejJUzkyMsqYo2 3BNGaD6rBHVKjN1eeWN3d3SvxY5MlynKEI8hPWrYD89c2qawHaaJFWHxtgGwcelSNtwo CxvRdHxgB9UBA1yJ/qFmyGjkVXcI0mvERL3mnmhzC/C7y+C53Q96d4kwWKrhYLwP8rxo eCIS8QTjlBr27FDDINdjhvYGgRSQb14fPIWQLl92Frf3HFsVDGU/SOji65IuLZms2rt1 BIVGnYVaDAgYJ4PQGqSA9DIiHaYUT0anDaPgMjWRVlDR3zwoWUSQhl4XgjGxSnKXmprb NA== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by userp2130.oracle.com with ESMTP id 2xf74s0vcd-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Jan 2020 18:44:04 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 00DIhpix077970; Mon, 13 Jan 2020 18:44:04 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 2xfqu50evu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Jan 2020 18:44:04 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 00DIhEAn028860; Mon, 13 Jan 2020 18:43:14 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 13 Jan 2020 10:43:14 -0800 Subject: Re: [PATCH v9 1/8] hugetlb_cgroup: Add hugetlb_cgroup reservation counter To: Mina Almasry Cc: shuah@kernel.org, rientjes@google.com, shakeelb@google.com, 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, mkoutny@suse.com, Hillf Danton References: <20191217231615.164161-1-almasrymina@google.com> From: Mike Kravetz Message-ID: <817e2c4b-4c72-09f9-22ea-bbaf97584161@oracle.com> Date: Mon, 13 Jan 2020 10:43:12 -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: <20191217231615.164161-1-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=9499 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-2001130151 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9499 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-2001130151 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 12/17/19 3:16 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 allocate 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 allocate hugetlb memory only more 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. > > We have developers interested in using hugetlb_cgroups, and they have expressed > dissatisfaction regarding this behavior. We'd like to improve this > behavior such that tasks 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. > > 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]_in_bytes. This > counter has slightly different semantics than > hugetlb.xMB.[limit|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. To me, this implies that 'faults without reservations' could cause reservation usage to exceed reservation limit? Or, does the faulting process get a SIGBUS because of the reservation limit even though it is not using reservations? We shall see in subsequent patches. > > - 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. We also added cgroup-v2 support to > hugetlb_cgroup so that the new use cases can be extended to v2. As previously discussed, cgroup-v2 support for hugetlb_cgroup will exist before this patch series. > > 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 > Acked-by: Hillf Danton I think the ACK by Hillf happened some time back. You may want to check to see if it still applies. > > --- > include/linux/hugetlb.h | 4 +- > mm/hugetlb_cgroup.c | 116 +++++++++++++++++++++++++++++++++++----- > 2 files changed, 106 insertions(+), 14 deletions(-) Only one minor nit in the code. You made this cleanup, @@ -472,7 +519,7 @@ static void __init __hugetlb_cgroup_file_dfl_init(int idx) struct hstate *h = &hstates[idx]; /* format the size */ - mem_fmt(buf, 32, huge_page_size(h)); + mem_fmt(buf, sizeof(buf), huge_page_size(h)); /* Add the limit file */ cft = &h->cgroup_files_dfl[0]; But did not make the same cleanup in __hugetlb_cgroup_file_legacy_init() -- Mike Kravetz