From patchwork Mon Aug 26 23:32:40 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mina Almasry X-Patchwork-Id: 11115801 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9ABD714F7 for ; Mon, 26 Aug 2019 23:33:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5A9CE2189D for ; Mon, 26 Aug 2019 23:33:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="BfXwwjAu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5A9CE2189D Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C10A26B0291; Mon, 26 Aug 2019 19:33:18 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id B9A816B0292; Mon, 26 Aug 2019 19:33:18 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A874C6B0293; Mon, 26 Aug 2019 19:33:18 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 85C386B0291 for ; Mon, 26 Aug 2019 19:33:18 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 3B5B9180AD804 for ; Mon, 26 Aug 2019 23:33:18 +0000 (UTC) X-FDA: 75866182476.22.skirt87_39e4d6c255917 X-Spam-Summary: 2,0,0,2f6b17d53ff22f99,d41d8cd98f00b204,3pgxkxqskcjc1cd1jipd9e17ff7c5.3fdc9elo-ddbm13b.fi7@flex--almasrymina.bounces.google.com,:mike.kravetz@oracle.com:shuah@kernel.org:almasrymina@google.com:rientjes@google.com:shakeelb@google.com:gthelen@google.com:akpm@linux-foundation.org:khalid.aziz@oracle.com:linux-kernel@vger.kernel.org::linux-kselftest@vger.kernel.org:cgroups@vger.kernel.org:aneesh.kumar@linux.vnet.ibm.com:mkoutny@suse.com,RULES_HIT:2:41:152:355:379:541:960:973:988:989:1260:1277:1313:1314:1345:1359:1437:1516:1518:1535:1593:1594:1605:1606:1730:1747:1777:1792:1801:2198:2199:2393:2553:2559:2562:2693:2899:2901:3138:3139:3140:3141:3142:3152:3865:3866:3867:3868:3870:3871:3872:3873:3874:4119:4250:4321:4605:5007:6119:6261:6630:6653:6742:7875:7903:7904:9592:9969:10004:11026:11232:11658:11914:12043:12296:12297:12438:12555:12895:12986:13851:14096:14097:14394:14659:21080:21220:21444:21627:30034:30054:30090,0,RBL:209.85.160.202:@flex--almasrymina.bounces.google.co m:.lbl8. X-HE-Tag: skirt87_39e4d6c255917 X-Filterd-Recvd-Size: 8847 Received: from mail-qt1-f202.google.com (mail-qt1-f202.google.com [209.85.160.202]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Mon, 26 Aug 2019 23:33:17 +0000 (UTC) Received: by mail-qt1-f202.google.com with SMTP id g33so19153579qtc.14 for ; Mon, 26 Aug 2019 16:33:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=5FDOwwCe+APWdEQQqNbBpE6iIki5NU5vXPefDHikBmg=; b=BfXwwjAuhrLzwyV49VnJL7NxDepEgABTklx9qhc6rCK5F1w2xw2LFgmzTWfEAHiPTF c5v46KJZa6ts7LaEAl2UEDScmWBYH5FdRRkicG6JhCd5gzMC/MBrJM+gYNO8Y0DVWbd5 NXpoHq7M83Am1Y0GWNerd7Jl1ueGsflkoKLPII48XaDmWf1gZAsG9uA8s1QmT0b9GiBR N55L5aExlS7kaRIdXdaPfI1XlO+g1o6LMycyymR5h1zGtC9eyWIzaUH81AY7A3AqGLvk we6DYp4QKXYWKwHLDCaThtFG284KWl3dBsOd8oJmCEJHfUQZs3Chk6Cz9lgq6vY8+BVj jxoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=5FDOwwCe+APWdEQQqNbBpE6iIki5NU5vXPefDHikBmg=; b=HA5SZxCBf+glSs1maFdWZWirbajtg7uMl65ueA55N3RtacR0Rdf5F0Sl6o3aktzQz8 HSz24TxwTkicqbXKTcx1hyok8vy+GBPhKzEAt1zblyjw6xQ+VpZY7Q6Gj3m2rW5Po54m kpX/zLeFaZMiw1d9em6XXOH9fX42ifuzjoKhxaQWew9abjAdn8T7pP3pmOjkCKsLAtwK RFsluw4iTiuyOhkyHWYxsy8na9JJENGnwBBdYWss+xu6lsf+NTAoI4/J6Pm8uvxq3179 l/oYlWLBKGM0Woa8QcSwt1IRiUUO5ABwv0AdmjzChA3MaI3dJXTMIQm1p+c77fThkHis 4zmg== X-Gm-Message-State: APjAAAU3pFWnMXkxvlzu1Yf0BIwl1xJ9Hd4FBiRF2wFUhyWREXmX2wYj ClyGdA0Bc0nn9MHiZvvicdke7uNyLWmeo3jK+Q== X-Google-Smtp-Source: APXvYqyDImAPzfr0N58wa/tY2W7Edq/krF5d6f1tRQcHXjvREDYlfn3oZlUNIZ7WqjjdFcG1GxtewDdCNH22t72/9w== X-Received: by 2002:ad4:45d3:: with SMTP id v19mr17564793qvt.90.1566862396925; Mon, 26 Aug 2019 16:33:16 -0700 (PDT) Date: Mon, 26 Aug 2019 16:32:40 -0700 In-Reply-To: <20190826233240.11524-1-almasrymina@google.com> Message-Id: <20190826233240.11524-7-almasrymina@google.com> Mime-Version: 1.0 References: <20190826233240.11524-1-almasrymina@google.com> X-Mailer: git-send-email 2.23.0.187.g17f5b7556c-goog Subject: [PATCH v3 6/6] hugetlb_cgroup: Add hugetlb_cgroup reservation docs From: Mina Almasry To: mike.kravetz@oracle.com Cc: shuah@kernel.org, almasrymina@google.com, rientjes@google.com, shakeelb@google.com, gthelen@google.com, akpm@linux-foundation.org, khalid.aziz@oracle.com, 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Add docs for how to use hugetlb_cgroup reservations, and their behavior. --- .../admin-guide/cgroup-v1/hugetlb.rst | 84 ++++++++++++++++--- 1 file changed, 73 insertions(+), 11 deletions(-) -- 2.23.0.187.g17f5b7556c-goog diff --git a/Documentation/admin-guide/cgroup-v1/hugetlb.rst b/Documentation/admin-guide/cgroup-v1/hugetlb.rst index a3902aa253a96..cc6eb859fc722 100644 --- a/Documentation/admin-guide/cgroup-v1/hugetlb.rst +++ b/Documentation/admin-guide/cgroup-v1/hugetlb.rst @@ -2,13 +2,6 @@ HugeTLB Controller ================== -The HugeTLB controller allows to limit the HugeTLB usage per control group and -enforces the controller limit during page fault. Since HugeTLB doesn't -support page reclaim, enforcing the limit at page fault time implies that, -the application will get SIGBUS signal if it tries to access HugeTLB pages -beyond its limit. This requires the application to know beforehand how much -HugeTLB pages it would require for its use. - HugeTLB controller can be created by first mounting the cgroup filesystem. # mount -t cgroup -o hugetlb none /sys/fs/cgroup @@ -28,10 +21,14 @@ process (bash) into it. Brief summary of control files:: - hugetlb..limit_in_bytes # set/show limit of "hugepagesize" hugetlb usage - hugetlb..max_usage_in_bytes # show max "hugepagesize" hugetlb usage recorded - hugetlb..usage_in_bytes # show current usage for "hugepagesize" hugetlb - hugetlb..failcnt # show the number of allocation failure due to HugeTLB limit + hugetlb..reservation_limit_in_bytes # set/show limit of "hugepagesize" hugetlb reservations + hugetlb..reservation_max_usage_in_bytes # show max "hugepagesize" hugetlb reservations recorded + hugetlb..reservation_usage_in_bytes # show current reservations for "hugepagesize" hugetlb + hugetlb..reservation_failcnt # show the number of allocation failure due to HugeTLB reservation limit + hugetlb..limit_in_bytes # set/show limit of "hugepagesize" hugetlb faults + hugetlb..max_usage_in_bytes # show max "hugepagesize" hugetlb usage recorded + hugetlb..usage_in_bytes # show current usage for "hugepagesize" hugetlb + hugetlb..failcnt # show the number of allocation failure due to HugeTLB usage limit For a system supporting three hugepage sizes (64k, 32M and 1G), the control files include:: @@ -40,11 +37,76 @@ files include:: hugetlb.1GB.max_usage_in_bytes hugetlb.1GB.usage_in_bytes hugetlb.1GB.failcnt + hugetlb.1GB.reservation_limit_in_bytes + hugetlb.1GB.reservation_max_usage_in_bytes + hugetlb.1GB.reservation_usage_in_bytes + hugetlb.1GB.reservation_failcnt hugetlb.64KB.limit_in_bytes hugetlb.64KB.max_usage_in_bytes hugetlb.64KB.usage_in_bytes hugetlb.64KB.failcnt + hugetlb.64KB.reservation_limit_in_bytes + hugetlb.64KB.reservation_max_usage_in_bytes + hugetlb.64KB.reservation_usage_in_bytes + hugetlb.64KB.reservation_failcnt hugetlb.32MB.limit_in_bytes hugetlb.32MB.max_usage_in_bytes hugetlb.32MB.usage_in_bytes hugetlb.32MB.failcnt + hugetlb.32MB.reservation_limit_in_bytes + hugetlb.32MB.reservation_max_usage_in_bytes + hugetlb.32MB.reservation_usage_in_bytes + hugetlb.32MB.reservation_failcnt + + +1. Reservation limits + +The HugeTLB controller allows to limit the HugeTLB reservations per control +group and enforces the controller limit at reservation time. Reservation limits +are superior to Page fault limits (see section 2), since Reservation limits are +enforced at reservation time, and never causes the application to get SIGBUS +signal. Instead, if the application is violating its limits, then it gets an +error on reservation time, i.e. the mmap or shmget return an error. + + +2. Page fault limits + +The HugeTLB controller allows to limit the HugeTLB usage (page fault) per +control group and enforces the controller limit during page fault. Since HugeTLB +doesn't support page reclaim, enforcing the limit at page fault time implies +that, the application will get SIGBUS signal if it tries to access HugeTLB +pages beyond its limit. This requires the application to know beforehand how +much HugeTLB pages it would require for its use. + + +3. Caveats with shared memory + +a. Charging and uncharging: + +For shared hugetlb memory, both hugetlb reservation and usage (page faults) are +charged to the first task that causes the memory to be reserved or faulted, +and all subsequent uses of this reserved or faulted memory is done without +charging. + +Shared hugetlb memory is only uncharged when it is unreseved or deallocated. +This is usually when the hugetlbfs file is deleted, and not when the task that +caused the reservation or fault has exited. + +b. Interaction between reservation limit and fault limit. + +Generally, it's not recommended to set both of the reservation limit and fault +limit in a cgroup. For private memory, the fault usage cannot exceed the +reservation usage, so if you set both, one of those limits will be useless. + +For shared memory, a cgroup's fault usage may be greater than its reservation +usage, so some care needs to be taken. Consider this example: + +- Task A reserves 4 pages in a shared hugetlbfs file. Cgroup A will get + 4 reservations charged to it and no faults charged to it. +- Task B reserves and faults the same 4 pages as Task A. Cgroup B will get no + reservation charge, but will get charged 4 faulted pages. If Cgroup B's limit + is less than 4, then Task B will get a SIGBUS. + +For the above scenario, it's not recommended for the userspace to set both +reservation limits and fault limits, but it is still allowed to in case it sees +some use for it.