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[35.185.212.55]) by smtp.gmail.com with ESMTPSA id x9-20020a17090a294900b001eaae89de5fsm2147169pjf.1.2022.06.29.07.01.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Jun 2022 07:01:39 -0700 (PDT) Date: Wed, 29 Jun 2022 07:01:36 -0700 From: Zach O'Keefe To: songliubraving@fb.com, willy@infradead.org, shy828301@gmail.com, linmiaohe@huawei.com Cc: linux-mm@kvack.org Subject: thp: enforcing constraints on file thps Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656511301; a=rsa-sha256; cv=none; b=EwuSEOCY3uOPxD56Hm8zfXRFt4rDHm2xUQX8a//WHtWbMbVkwZfbQ/XCuAcDSaxkGH8GY3 tyHA0X46NkzvpZA4dW+v3afn4lTNLRe/C28wdphzNAvEe8tR2ly2gzYc2g1rF3De0dMYD0 65O0R8Cj5S6d0RYjcMPStm1dDUd44x8= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=UbJIaPi6; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf24.hostedemail.com: domain of zokeefe@google.com designates 209.85.216.48 as permitted sender) smtp.mailfrom=zokeefe@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656511301; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding:in-reply-to: references:dkim-signature; bh=1rrTNnCWA05ZUIhKtkdtBmwJWbPispxQpokjnYw4XpA=; b=56AzdCTtSUQbrqCHQluzeTlMlxO9pchEXd4ZQyBWmJmydpMou5RbRXqXuQCJlLlr5qT7sm PzkumYUF9x8MdxYHyrd3u5iaAEXNGA9dBpPBms+cixOd/aPUM8vENYiqxR3tTRWU9vDqBe L8fNGAngnHcZGCo7mBnCg+EyC4UWXk8= X-Stat-Signature: ei9fwo3oa3u15kgqweath1ycayoz4thn X-Rspamd-Queue-Id: ABAA31800B3 Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=UbJIaPi6; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf24.hostedemail.com: domain of zokeefe@google.com designates 209.85.216.48 as permitted sender) smtp.mailfrom=zokeefe@google.com X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1656511301-460961 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: Hey All, There are currently a number of paths where we can collapse file memory into THPs: 1a) khugepaged - target of vma being processed 1b) khugepaged - other vma found mapping file, able to lock mmap_lock in retract_page_tables() 1b) khugepaged - other vma found mapping file, deferred pte-mapped THP collapse, processed in collapse_pte_mapped_thp() 2) page fault finds hugepage in page cache + filemap_map_pages() In terms of system-enforced THP constraints: * vma flags + thps sysfs settings Checked in 1a. (1b now at least respects "never" THP mode after Yang Shi's cleanup series, but still doesn't respect "madvise" THP mode) * MMF_DISABLE_THP Checked in 1a and 1b I'm wondering if we should align these, and if so, in what direction? I would argue that a process marked MMF_DISABLE_THP, or a vma marked VM_NOHUGEPAGE, probably shouldn't be mapping at the pmd level, and that the appropriate checks should be added in those paths. Thanks, Zach