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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=ham 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 5BF5FC35249 for ; Mon, 3 Feb 2020 23:23:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 035A320720 for ; Mon, 3 Feb 2020 23:23:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lJWoiLvA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 035A320720 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 AADBA6B0266; Mon, 3 Feb 2020 18:23:34 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A34896B0269; Mon, 3 Feb 2020 18:23:34 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 922D26B026A; Mon, 3 Feb 2020 18:23:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0222.hostedemail.com [216.40.44.222]) by kanga.kvack.org (Postfix) with ESMTP id 76A9E6B0266 for ; Mon, 3 Feb 2020 18:23:34 -0500 (EST) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 24D198248047 for ; Mon, 3 Feb 2020 23:23:34 +0000 (UTC) X-FDA: 76450394748.26.comb73_1f12548219123 X-HE-Tag: comb73_1f12548219123 X-Filterd-Recvd-Size: 10191 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Mon, 3 Feb 2020 23:23:33 +0000 (UTC) Received: by mail-pf1-f202.google.com with SMTP id r29so10293229pfl.23 for ; Mon, 03 Feb 2020 15:23:33 -0800 (PST) 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=Rh1VpC3lsdIyERHgh3jf8eKCiFmpm7UqZQ8YvTrqfM4=; b=lJWoiLvA5ULX2YkzsX59NYhbVWkttrtaHjNvm+zEAsK007W39kDP276kPfC/zR+NtU aePkES0Rxh5xuYJ0x7300FCQN9Q7L/hKYezwbrxsdRe39AcNr5SKgiG6eccjEfZ8+dvw JCn8Gmz4+W0picdlbmEZiN0L7LxhEsSemsiXX+3rwXMUf++r39DrPjtPJBTX6e+UF5he W3sQ8KRPRyTetp1On8GbNCyrreub4TaeVJ8sFff84dJ+7lh9zCh/DF3SYI5+LncPzWpl if9Qf6Qf26NXkRPufOS7uofgDKn370jEFmEJnxfQbhIyyfQyvjgByJSrliDxrBevdTb8 NvVg== 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=Rh1VpC3lsdIyERHgh3jf8eKCiFmpm7UqZQ8YvTrqfM4=; b=hOyxXQWggoa4CE05/IdzEL8faPyyDZZWHWGAipbGeuVWvuw0nYNiJoAVSgrE3GtY+v 2jgOI2SQEbkif01P0yx0Ity5VnPDAq/ZtHI+eUSDnw4vzrl39LuVYe9JkD3B5wrOJu6E Zr0NK1zCUVZ+SeqGtvcM/XMZuF5sCLT9Fd0zsjkN7IE5mHn0baZwSg5l01UbZTl0zSXv wxAO+/toXlEMezWpwcYCiMMeK3Hom+mcqWhpK5+YRwbfOrOgaW5T1yiZTv0ZkCww/CrZ T0y7nRnGwJB1XvNnK7Vu/3NMp1nwqLSGWlX0Wk3LyynZN6QlUeFVwSpbcib7zung08FF evqA== X-Gm-Message-State: APjAAAXEaly/YKGY9wGMwGvu4eXU+3sn/pKn+ur6BgR/9RF2t1igEWwc YeDH2zoDzS2RTJaVRw/xla1BRRM8xnrDYtnynQ== X-Google-Smtp-Source: APXvYqyekQ/PTvIbKgAeQuqpAu36PLUFRW8ivPd8SpnZY9lBMOLs4YjQ+LBgcv2HhoAHddwfBPPKUnTSwWhf0kgjhQ== X-Received: by 2002:a63:6787:: with SMTP id b129mr28057788pgc.103.1580772212242; Mon, 03 Feb 2020 15:23:32 -0800 (PST) Date: Mon, 3 Feb 2020 15:22:48 -0800 In-Reply-To: <20200203232248.104733-1-almasrymina@google.com> Message-Id: <20200203232248.104733-9-almasrymina@google.com> Mime-Version: 1.0 References: <20200203232248.104733-1-almasrymina@google.com> X-Mailer: git-send-email 2.25.0.341.g760bfbb309-goog Subject: [PATCH v11 9/9] 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, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org Content-Type: text/plain; charset="UTF-8" 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. Signed-off-by: Mina Almasry --- Changes in v11: - Changed resv.* to rsvd.* Changes in v10: - Clarify reparenting behavior. - Reword benefits of reservation limits. Changes in v6: - Updated docs to reflect the new design based on a new counter that tracks both reservations and faults. --- .../admin-guide/cgroup-v1/hugetlb.rst | 103 ++++++++++++++++-- 1 file changed, 92 insertions(+), 11 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v1/hugetlb.rst b/Documentation/admin-guide/cgroup-v1/hugetlb.rst index a3902aa253a96..338f2c7d7a1cd 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..rsvd.limit_in_bytes # set/show limit of "hugepagesize" hugetlb reservations + hugetlb..rsvd.max_usage_in_bytes # show max "hugepagesize" hugetlb reservations and no-reserve faults + hugetlb..rsvd.usage_in_bytes # show current reservations and no-reserve faults for "hugepagesize" hugetlb + hugetlb..rsvd.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 +37,95 @@ files include:: hugetlb.1GB.max_usage_in_bytes hugetlb.1GB.usage_in_bytes hugetlb.1GB.failcnt + hugetlb.1GB.rsvd.limit_in_bytes + hugetlb.1GB.rsvd.max_usage_in_bytes + hugetlb.1GB.rsvd.usage_in_bytes + hugetlb.1GB.rsvd.failcnt hugetlb.64KB.limit_in_bytes hugetlb.64KB.max_usage_in_bytes hugetlb.64KB.usage_in_bytes hugetlb.64KB.failcnt + hugetlb.64KB.rsvd.limit_in_bytes + hugetlb.64KB.rsvd.max_usage_in_bytes + hugetlb.64KB.rsvd.usage_in_bytes + hugetlb.64KB.rsvd.failcnt hugetlb.32MB.limit_in_bytes hugetlb.32MB.max_usage_in_bytes hugetlb.32MB.usage_in_bytes hugetlb.32MB.failcnt + hugetlb.32MB.rsvd.limit_in_bytes + hugetlb.32MB.rsvd.max_usage_in_bytes + hugetlb.32MB.rsvd.usage_in_bytes + hugetlb.32MB.rsvd.failcnt + + +1. Page fault accounting + +hugetlb..limit_in_bytes +hugetlb..max_usage_in_bytes +hugetlb..usage_in_bytes +hugetlb..failcnt + +The HugeTLB controller allows users to limit the HugeTLB usage (page fault) per +control group and enforces the 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 fault in HugeTLB +pages beyond its limit. Therefore the application needs to know exactly how many +HugeTLB pages it uses before hand, and the sysadmin needs to make sure that +there are enough available on the machine for all the users to avoid processes +getting SIGBUS. + + +2. Reservation accounting + +hugetlb..rsvd.limit_in_bytes +hugetlb..rsvd.max_usage_in_bytes +hugetlb..rsvd.usage_in_bytes +hugetlb..rsvd.failcnt + +The HugeTLB controller allows to limit the HugeTLB reservations per control +group and enforces the controller limit at reservation time and at the fault of +HugeTLB memory for which no reservation exists. Since reservation limits are +enforced at reservation time (on mmap or shget), reservation limits never causes +the application to get SIGBUS signal if the memory was reserved before hand. For +MAP_NORESERVE allocations, the reservation limit behaves the same as the fault +limit, enforcing memory usage at fault time and causing the application to +receive a SIGBUS if it's crossing its limit. + +Reservation limits are superior to page fault limits described above, since +reservation limits are enforced at reservation time (on mmap or shget), and +never causes the application to get SIGBUS signal if the memory was reserved +before hand. This allows for easier fallback to alternatives such as +non-HugeTLB memory for example. In the case of page fault accounting, it's very +hard to avoid processes getting SIGBUS since the sysadmin needs precisely know +the HugeTLB usage of all the tasks in the system and make sure there is enough +pages to satisfy all requests. Avoiding tasks getting SIGBUS on overcommited +systems is practically impossible with page fault accounting. + + +3. Caveats with shared memory + +For shared HugeTLB memory, both HugeTLB reservation and 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 unreserved or deallocated. +This is usually when the HugeTLB file is deleted, and not when the task that +caused the reservation or fault has exited. + + +4. Caveats with HugeTLB cgroup offline. + +When a HugeTLB cgroup goes offline with some reservations or faults still +charged to it, the behavior is as follows: + +- The fault charges are charged to the parent HugeTLB cgroup (reparented), +- the reservation charges remain on the offline HugeTLB cgroup. + +This means that if a HugeTLB cgroup gets offlined while there is still HugeTLB +reservations charged to it, that cgroup persists as a zombie until all HugeTLB +reservations are uncharged. HugeTLB reservations behave in this manner to match +the memory controller whose cgroups also persist as zombie until all charged +memory is uncharged. Also, the tracking of HugeTLB reservations is a bit more +complex compared to the tracking of HugeTLB faults, so it is significantly +harder to reparent reservations at offline time. -- 2.25.0.341.g760bfbb309-goog