From patchwork Tue Nov 23 00:01:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mina Almasry X-Patchwork-Id: 12633221 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 94395C433F5 for ; Tue, 23 Nov 2021 00:01:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0E0496B0072; Mon, 22 Nov 2021 19:01:18 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 091166B0073; Mon, 22 Nov 2021 19:01:18 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E73766B0074; Mon, 22 Nov 2021 19:01:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0110.hostedemail.com [216.40.44.110]) by kanga.kvack.org (Postfix) with ESMTP id D724E6B0072 for ; Mon, 22 Nov 2021 19:01:17 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A740A886CF for ; Tue, 23 Nov 2021 00:01:07 +0000 (UTC) X-FDA: 78838239774.03.1E005C3 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) by imf21.hostedemail.com (Postfix) with ESMTP id 723B6D0369F3 for ; Tue, 23 Nov 2021 00:01:05 +0000 (UTC) Received: by mail-pj1-f73.google.com with SMTP id lt10-20020a17090b354a00b001a649326aedso420686pjb.5 for ; Mon, 22 Nov 2021 16:01:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=c5/tpWSff4dFHh5q6xjJHceDD7GLZ6RDhs8W9YIAjtE=; b=qhWa4Zhk7NchUhmumrVqvSAJuvqQCaRNgR3VhkJ1cgKkIgT3PnHJcxg50Bf/bvcBWt B03yUWlvIhJT0+svy9+S95w02WodOrWOwkw5zEquFIWPBU1l2w1CU7Z6SunbYgyeaykD s996BxASMp47tXiGEFsA9XFGGfjUhPiOjd5sWt5YfXx/RvgMTswVOyEFMuhEg2iC5Adx 6+ysqnul60O+2OJzTLAjf4CFIj4TQV0rDQNETBIJgTDohirT10IhjQPH532Pn59O1ID0 N50qA7HX83qIC2v7mwBK9B04GibyR4v/fffAzRRrTrmFPY3jEDG+KTy2R0ntAim9z/uJ 1fPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=c5/tpWSff4dFHh5q6xjJHceDD7GLZ6RDhs8W9YIAjtE=; b=U1mFbuFKADFDnx4eGUGlTAqBZ4BdPiFjhAeRdw5VvBdj0bnV5R2Ww+Qr+SKDnI+QO/ LAC0TAu0TAjYApbAs3UmJF22Rst7/cwgGCR0eIsA2xS5lQ9ud+BwwAkanwk7lO+aA9vM qy3o2+ym/xsmljqZYpJlkpoX50nNOzuoVuAiVvLaLb5P3gbai9HfAazkQ21Z9a7LnKJh +jyS/gt2WbSRUJntom+7VNVqcx7axpMTADj96ht5gnQaELPlfqGxoBMIUoywlBZV8wXb /eOch6n8+8QaXqrDaBvQy5RixHv4lVvJnCTaG/wbaRdoNhaJtmCsBOOO4qpLYFuB3s8m 6QAw== X-Gm-Message-State: AOAM530DQtZ+IMq97O863s6tMitOm63GfZYLBbECpS5AOzvQKfCLnrOv mrYSzP4Rxvxdo+2aQuD5QzcZibtDYzlzawUq4A== X-Google-Smtp-Source: ABdhPJxCARKpo3QKn92oJKAmEFehwZ16v8foZGYajsmSBMeZsEGa8Zj7R770PBjkFSHsamA67kz2cPaXIlGU69lLmw== X-Received: from almasrymina.svl.corp.google.com ([2620:15c:2cd:202:2c06:26c4:bf33:6d15]) (user=almasrymina job=sendgmr) by 2002:a05:6a00:1705:b0:4a0:3492:16c with SMTP id h5-20020a056a00170500b004a03492016cmr928900pfc.3.1637625666001; Mon, 22 Nov 2021 16:01:06 -0800 (PST) Date: Mon, 22 Nov 2021 16:01:02 -0800 Message-Id: <20211123000102.4052105-1-almasrymina@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.34.0.rc2.393.gf8c9666880-goog Subject: [PATCH v7] mm: Add PM_THP_MAPPED to /proc/pid/pagemap From: Mina Almasry To: Jonathan Corbet Cc: Mina Almasry , David Hildenbrand , Matthew Wilcox , "Paul E . McKenney" , Yu Zhao , Andrew Morton , Peter Xu , Ivan Teterevkov , Florian Schmidt , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org X-Stat-Signature: t3eod57k7q5efxcjfcb95djwtwa8o5y6 Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=qhWa4Zhk; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf21.hostedemail.com: domain of 3Qi-cYQsKCCUBMNBTSZNJOBHPPHMF.DPNMJOVY-NNLWBDL.PSH@flex--almasrymina.bounces.google.com designates 209.85.216.73 as permitted sender) smtp.mailfrom=3Qi-cYQsKCCUBMNBTSZNJOBHPPHMF.DPNMJOVY-NNLWBDL.PSH@flex--almasrymina.bounces.google.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 723B6D0369F3 X-HE-Tag: 1637625665-669474 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 PM_THP_MAPPED MAPPING to allow userspace to detect whether a given virt address is currently mapped by a transparent huge page or not. Example use case is a process requesting THPs from the kernel (via a huge tmpfs mount for example), for a performance critical region of memory. The userspace may want to query whether the kernel is actually backing this memory by hugepages or not. PM_THP_MAPPED bit is set if the virt address is mapped at the PMD level and the underlying page is a transparent huge page. A few options were considered: 1. Add /proc/pid/pageflags that exports the same info as /proc/kpageflags. This is not appropriate because many kpageflags are inappropriate to expose to userspace processes. 2. Simply get this info from the existing /proc/pid/smaps interface. There are a couple of issues with that: 1. /proc/pid/smaps output is human readable and unfriendly to programatically parse. 2. /proc/pid/smaps is slow because it must read the whole memory range rather than a small range we care about. The cost of reading /proc/pid/smaps into userspace buffers is about ~800us per call, and this doesn't include parsing the output to get the information you need. The cost of querying 1 virt address in /proc/pid/pagemaps however is around 5-7us. Tested manually by adding logging into transhuge-stress, and by allocating THP and querying the PM_THP_MAPPED flag at those virtual addresses. Signed-off-by: Mina Almasry Cc: David Hildenbrand Cc: Matthew Wilcox Cc: David Rientjes rientjes@google.com Cc: Paul E. McKenney Cc: Yu Zhao Cc: Jonathan Corbet Cc: Andrew Morton Cc: Peter Xu Cc: Ivan Teterevkov Cc: Florian Schmidt Cc: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Acked-by: Peter Xu Acked-by: David Rientjes Reviewed-by: David Hildenbrand --- Changes in v7: - Added clarification that smaps is only slow because it looks at the whole address space. Changes in v6: - Renamed to PM_THP_MAPPED - Removed changes to transhuge-stress Changes in v5: - Added justification for this interface in the commit message! Changes in v4: - Removed unnecessary moving of flags variable declaration Changes in v3: - Renamed PM_THP to PM_HUGE_THP_MAPPING - Fixed checks to set PM_HUGE_THP_MAPPING - Added PM_HUGE_THP_MAPPING docs --- Documentation/admin-guide/mm/pagemap.rst | 3 ++- fs/proc/task_mmu.c | 3 +++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst index fdc19fbc10839..8a0f0064ff336 100644 --- a/Documentation/admin-guide/mm/pagemap.rst +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -23,7 +23,8 @@ There are four components to pagemap: * Bit 56 page exclusively mapped (since 4.2) * Bit 57 pte is uffd-wp write-protected (since 5.13) (see :ref:`Documentation/admin-guide/mm/userfaultfd.rst `) - * Bits 57-60 zero + * Bit 58 page is a huge (PMD size) THP mapping + * Bits 59-60 zero * Bit 61 page is file-page or shared-anon (since 3.5) * Bit 62 page swapped * Bit 63 page present diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index ad667dbc96f5c..d784a97aa209a 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1302,6 +1302,7 @@ struct pagemapread { #define PM_SOFT_DIRTY BIT_ULL(55) #define PM_MMAP_EXCLUSIVE BIT_ULL(56) #define PM_UFFD_WP BIT_ULL(57) +#define PM_THP_MAPPED BIT_ULL(58) #define PM_FILE BIT_ULL(61) #define PM_SWAP BIT_ULL(62) #define PM_PRESENT BIT_ULL(63) @@ -1456,6 +1457,8 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, if (page && page_mapcount(page) == 1) flags |= PM_MMAP_EXCLUSIVE; + if (page && is_transparent_hugepage(page)) + flags |= PM_THP_MAPPED; for (; addr != end; addr += PAGE_SIZE) { pagemap_entry_t pme = make_pme(frame, flags);