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=-23.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 4CF94C433DB for ; Tue, 2 Feb 2021 22:13:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C06B864DDB for ; Tue, 2 Feb 2021 22:12:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C06B864DDB 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 403EF6B006C; Tue, 2 Feb 2021 17:12:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3B6B46B006E; Tue, 2 Feb 2021 17:12:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2CD376B0070; Tue, 2 Feb 2021 17:12:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0089.hostedemail.com [216.40.44.89]) by kanga.kvack.org (Postfix) with ESMTP id 17F216B006C for ; Tue, 2 Feb 2021 17:12:59 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D29E73632 for ; Tue, 2 Feb 2021 22:12:58 +0000 (UTC) X-FDA: 77774728836.02.wing27_620aade275ce Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id B415310097AA2 for ; Tue, 2 Feb 2021 22:12:58 +0000 (UTC) X-HE-Tag: wing27_620aade275ce X-Filterd-Recvd-Size: 8767 Received: from mail-wr1-f44.google.com (mail-wr1-f44.google.com [209.85.221.44]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Tue, 2 Feb 2021 22:12:58 +0000 (UTC) Received: by mail-wr1-f44.google.com with SMTP id c12so22084238wrc.7 for ; Tue, 02 Feb 2021 14:12:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=xqP0a66Os6f9sXyF+kMsv13PEbv0LhzI8V6aeWIM0Ok=; b=TPz3NwZfJQX2n8XN2IcK3GG1+YdjmSwEfCGkkfB/R3l9sej3bWUpfbAM6RCQCZ7zSg wtMWuG93czJxsPaqc/vxVW5m5aofw7Xucq73fsummtWKzVU1OcRLPV1d4bpHrkbnQvc4 IGVMEw8sSzmZ9C62tJnk3nveiCu7uLVYsZYtvwViU06V6jZ65gHNw7E+q3Wxw3dk6eXe z5op6gObDb+ORYEdWZ3w4BYU3o2SvM5AHHBAGBxccLb/WJ/Qhq7WY8qKqMIPltmMJ5MP z66weUVMT+YCRplS4JltaxL/GEcdZbNO5Nz0syi3n8gD39XWVSSc8FUArjYvPDInNAiR z2yg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=xqP0a66Os6f9sXyF+kMsv13PEbv0LhzI8V6aeWIM0Ok=; b=Ff3WKVyMr3hHtw3qNcoTLyjuW/zsjEv74UiK2bAs/z2gT7gZHS54KY5IYn+73lqgfQ a2ICabBoSy62XW4n4rYSc4sJSY1ETNXjgk2m+bPjoF2CbKTE9f8kAOHFpRwlnQfblrwn dhanp/eDAPspGXw9EOht1c1Xc9BmU1VN/FSbjA1BxlNTBl8/pZThAhPfBslj4UYoLlQZ 8ZV48xzwj58friGH9mRV4acQBcCkaZB6XXobtImRp14EkRXetoDLF60QXlsEUlaBhXna CZzf8197G0oI77MYAsf3nKXXJrqOy2ddya80nRutTQdOV+GUoHAEK53ES1+esE4IcPx3 Ts5A== X-Gm-Message-State: AOAM5337YM/uRsfre5R/vwkjUhiq+lSxbaemystrKBex9g07ldWtxCkv 7WsuTmyr3iY0VCuR+rMg6J9Ud3bLwyB+JGCx46r//g== X-Google-Smtp-Source: ABdhPJzXdtevgSVe8n6EmjpNVas/jAjd+jbkaq+OR2OyjZFVqFMgbuoQU4zl5BsooeiKMks3pFo2re/Jz6z7ZkZVsLc= X-Received: by 2002:a5d:6884:: with SMTP id h4mr218812wru.106.1612303976784; Tue, 02 Feb 2021 14:12:56 -0800 (PST) MIME-Version: 1.0 References: <20210202053046.1653012-1-surenb@google.com> <079db245-a08c-0dbd-01d4-8065f533652e@gmail.com> In-Reply-To: <079db245-a08c-0dbd-01d4-8065f533652e@gmail.com> From: Suren Baghdasaryan Date: Tue, 2 Feb 2021 14:12:45 -0800 Message-ID: Subject: Re: [PATCH v3 1/1] process_madvise.2: Add process_madvise man page To: "Michael Kerrisk (man-pages)" Cc: linux-man , Andrew Morton , Jann Horn , Kees Cook , Jeffrey Vander Stoep , Minchan Kim , Michal Hocko , Shakeel Butt , David Rientjes , =?UTF-8?Q?Edgar_Arriaga_Garc=C3=ADa?= , Tim Murray , linux-mm , SElinux list , linux-security-module , Linux API , LKML , kernel-team 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: Hi Michael, On Tue, Feb 2, 2021 at 2:45 AM Michael Kerrisk (man-pages) wrote: > > Hello Suren (and Minchan and Michal) > > Thank you for the revisions! > > I've applied this patch, and done a few light edits. Thanks! > > However, I have a questions about undocumented pieces in *madvise(2)*, > as well as one other question. See below. > > On 2/2/21 6:30 AM, Suren Baghdasaryan wrote: > > Initial version of process_madvise(2) manual page. Initial text was > > extracted from [1], amended after fix [2] and more details added using > > man pages of madvise(2) and process_vm_read(2) as examples. It also > > includes the changes to required permission proposed in [3]. > > > > [1] https://lore.kernel.org/patchwork/patch/1297933/ > > [2] https://lkml.org/lkml/2020/12/8/1282 > > [3] https://patchwork.kernel.org/project/selinux/patch/20210111170622.2613577-1-surenb@google.com/#23888311 > > > > Signed-off-by: Suren Baghdasaryan > > Reviewed-by: Michal Hocko > > --- > > changes in v2: > > - Changed description of MADV_COLD per Michal Hocko's suggestion > > - Applied fixes suggested by Michael Kerrisk > > changes in v3: > > - Added Michal's Reviewed-by > > - Applied additional fixes suggested by Michael Kerrisk > > > > NAME > > process_madvise - give advice about use of memory to a process > > > > SYNOPSIS > > #include > > > > ssize_t process_madvise(int pidfd, > > const struct iovec *iovec, > > unsigned long vlen, > > int advice, > > unsigned int flags); > > > > DESCRIPTION > > The process_madvise() system call is used to give advice or directions > > to the kernel about the address ranges of another process or the calling > > process. It provides the advice to the address ranges described by iovec > > and vlen. The goal of such advice is to improve system or application > > performance. > > > > The pidfd argument is a PID file descriptor (see pidfd_open(2)) that > > specifies the process to which the advice is to be applied. > > > > The pointer iovec points to an array of iovec structures, defined in > > as: > > > > struct iovec { > > void *iov_base; /* Starting address */ > > size_t iov_len; /* Number of bytes to transfer */ > > }; > > > > The iovec structure describes address ranges beginning at iov_base address > > and with the size of iov_len bytes. > > > > The vlen represents the number of elements in the iovec structure. > > > > The advice argument is one of the values listed below. > > > > Linux-specific advice values > > The following Linux-specific advice values have no counterparts in the > > POSIX-specified posix_madvise(3), and may or may not have counterparts > > in the madvise(2) interface available on other implementations. > > > > MADV_COLD (since Linux 5.4.1) > > I just noticed these version numbers now, and thought: they can't be > right (because the system call appeared only in v5.11). So I removed > them. But, of course in another sense the version numbers are (nearly) > right, since these advice values were added for madvise(2) in Linux 5.4. > However, they are not documented in the madvise(2) manual page. Is it > correct to assume that MADV_COLD and MADV_PAGEOUT have exactly the same > meaning in madvise(2) (but just for the calling process, of course)? Correct. They should be added in the madvise(2) man page as well IMHO. > > > Deactive a given range of pages which will make them a more probable > > I changed: s/Deactive/Deactivate/ thanks! > > > reclaim target should there be a memory pressure. This is a > > nondestructive operation. The advice might be ignored for some pages > > in the range when it is not applicable. > > > > MADV_PAGEOUT (since Linux 5.4.1) > > Reclaim a given range of pages. This is done to free up memory occupied > > by these pages. If a page is anonymous it will be swapped out. If a > > page is file-backed and dirty it will be written back to the backing > > storage. The advice might be ignored for some pages in the range when > > it is not applicable. > > [...] > > > The hint might be applied to a part of iovec if one of its elements points > > to an invalid memory region in the remote process. No further elements will > > be processed beyond that point. > > Is the above scenario the one that leads to the partial advice case described in > RETURN VALUE? If yes, perhaps I should add some words to make that clearer. Correct. This describes the case when partial advice happens. > > You can see the light edits that I made in > https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=e3ce016472a1b3ec5dffdeb23c98b9fef618a97b > and following that I restructured DESCRIPTION a little in > https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=3aac0708a9acee5283e091461de6a8410bc921a6 The edits LGTM. Thanks, Suren. > > Thanks, > > Michael > > > -- > Michael Kerrisk > Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ > Linux/UNIX System Programming Training: http://man7.org/training/