From patchwork Tue Dec 17 23:16:15 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mina Almasry X-Patchwork-Id: 11299055 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 BBF9017F0 for ; Tue, 17 Dec 2019 23:16:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 90BC82467E for ; Tue, 17 Dec 2019 23:16:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Szx8Svtg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726734AbfLQXQj (ORCPT ); Tue, 17 Dec 2019 18:16:39 -0500 Received: from mail-pj1-f74.google.com ([209.85.216.74]:34758 "EHLO mail-pj1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726713AbfLQXQi (ORCPT ); Tue, 17 Dec 2019 18:16:38 -0500 Received: by mail-pj1-f74.google.com with SMTP id c67so536714pje.1 for ; Tue, 17 Dec 2019 15:16:36 -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=FDkTMVipAVEM2oYEaIDiMHcnRsGkEprqH/g1uso18v0=; b=Szx8SvtgGW397p6ntWPEc3OpmOTatK0fqb2QBbHtnTpfv1rzEt8maIi1s/Hfuw1VRm ZtB3AhgTUT9EmC5yHHgg3NsKkKJdxbchH2E/862SdXfeMDO+QiwWshasmmHEjTGL4+/3 rs+5Zpvg8cvQ/FW/2eNZ+bZl/QTVa8lsxcloMPCa6BMVmxDi5i85hIlpvxflSLJ2+DEV /h8lRdRwV/AuW+qiL06i0BvmgS7fYwgBcbfhX2AzHDGGV2Ox5huBqBira7KXoqG4Mx3C dHYx+JcGqZlUoldeOLyLVmFcLErBHFdRWY4ExU18KYOu0wxfTuo3VfuJg7wMexqMktda 4M5g== 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=FDkTMVipAVEM2oYEaIDiMHcnRsGkEprqH/g1uso18v0=; b=qY45LKBLtkHFsyyS2Q3FG7Tb+ifhO0fsc2d3GF6TOiykCTfrrzweU1JPqcsq6h97Uw 05Eqz9ceFNr2WWmaGzTT1IDNuiZ+iI7y+TvhrcEX0dA90mGEKTgDYhEWqwaoduB3rLRF 62ojIdMGq0jltI2Zf2psozB7oUD4vul6PeLKiicHcmoKKDdggxwG5IytYoXFx1TUu9MF vFnLMOIXvdVK1V8V6vbdtpRDN7ecWcl2tkXuG7fna+MAo5V5re4vFPyDdKvma88x+R3M oBa3iPQqX1jag+p9Tku8nDSkZEG/We2H4ywg5hVkvQbh7kyv0bosyNF7oK4sZu+2tJrD +tCA== X-Gm-Message-State: APjAAAVq9T413U0nfpz3N3lRX236HrA0GuGLlMXrSnDDKCO5pgByNbPv 68JTKZtaWsMAmo/SjIYsqVYXXurK+Jkxbkfl3Q== X-Google-Smtp-Source: APXvYqzwT3Z0rnODEkWeFuISUFMcJR8vLx9KJGGJxlN2WCBv1J/nE2VbtGHACnmLnrK21yQXTT5aweRVUSJiuRgH+Q== X-Received: by 2002:a63:1e23:: with SMTP id e35mr28758023pge.219.1576624596330; Tue, 17 Dec 2019 15:16:36 -0800 (PST) Date: Tue, 17 Dec 2019 15:16:15 -0800 In-Reply-To: <20191217231615.164161-1-almasrymina@google.com> Message-Id: <20191217231615.164161-8-almasrymina@google.com> Mime-Version: 1.0 References: <20191217231615.164161-1-almasrymina@google.com> X-Mailer: git-send-email 2.24.1.735.g03f4e72817-goog Subject: [PATCH v9 8/8] 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, aneesh.kumar@linux.vnet.ibm.com, mkoutny@suse.com, Hillf Danton Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add docs for how to use hugetlb_cgroup reservations, and their behavior. Signed-off-by: Mina Almasry Acked-by: Hillf Danton --- 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 | 64 +++++++++++++++---- 1 file changed, 53 insertions(+), 11 deletions(-) -- 2.24.1.735.g03f4e72817-goog diff --git a/Documentation/admin-guide/cgroup-v1/hugetlb.rst b/Documentation/admin-guide/cgroup-v1/hugetlb.rst index a3902aa253a96..efb94e4db9d5a 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 and no-reserve faults. + hugetlb..reservation_usage_in_bytes # show current reservations and no-reserve faults 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 +37,56 @@ 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 and at the fault of +hugetlb memory for which no reservation exists. Reservation limits +are superior to Page fault limits (see section 2), 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. 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. + +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 + +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 hugetlbfs file is deleted, and not when the task that +caused the reservation or fault has exited.