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=-23.3 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=unavailable 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 435E3C433E6 for ; Tue, 16 Feb 2021 17:48:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E55564E08 for ; Tue, 16 Feb 2021 17:48:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231387AbhBPRry (ORCPT ); Tue, 16 Feb 2021 12:47:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37202 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231142AbhBPRpr (ORCPT ); Tue, 16 Feb 2021 12:45:47 -0500 Received: from mail-wr1-x429.google.com (mail-wr1-x429.google.com [IPv6:2a00:1450:4864:20::429]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C44C7C06178B for ; Tue, 16 Feb 2021 09:44:26 -0800 (PST) Received: by mail-wr1-x429.google.com with SMTP id n4so11226507wrx.1 for ; Tue, 16 Feb 2021 09:44:26 -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=SG1PJqmUONPMltLHj/NtbdnqP3QjXhIMpbTG2ubKayU=; b=gJMg/HYjzxEkTtYwbl77f/5BHHhcOZMC+zF37X8B/qKaJjS1EDDbB5E9DQoW43x9Ek 76E252nanT1F78TvtOW336XdQ5XI2pgkFLuk8lV+8PGCPWvURVZ3vJclriyK4uwRFMuu xGfUjWRAT6bcrntxVeoXoOGx7MwnEXdAtpUU8ZO3L7o9N0UG9lCq4KjQ3HjAgCWQTSqh YN5i1/QKN0WwriXEcU452g8V07c3Z2gHHT9F0sAU9nYWOKC2FS6rNeX02IvXgCzbVWrr gpKWN5c2DYV9aBbrvqsHZss6UZMTz1bFiM1aDIiH1mOpVXo0SQte+allBrV+Wk/LWmiP 42VQ== 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=SG1PJqmUONPMltLHj/NtbdnqP3QjXhIMpbTG2ubKayU=; b=DGsnaGs50qvGk7RuSwjOKeEJyobAC0Qm+jH/m6YdUR0PXP1xgum1V7xtIOrjWnCQs3 /rz8GIgITVy5LTYEz/YCclmmfvq8Uh9+k4eN6/ZuMwOpMWIRs51w73XZwWnlAH6P+E5W ZxnMQW+UmXHQc7IPUXfBe5YcMKbbsJu2ORVgWvzT8lvgWEF0mnZflQ1rQryvsMzwyH1F CU/et4cjK0jiXcfsRyB0BfOSmKL2nHUdP0OG0E6JJkhVgoeqit7uxQoM5xANynMXJuLH LQj7J3QL0ICi5mKX+YNtk0iE9l1N60gTFIwSrF5y3CwYxTgOqT1hIqpI34ZA2XWvOkct avSg== X-Gm-Message-State: AOAM531V/GrZLgOVSn3S/FrTXsV5s+jKhZCBAGOOgGavDvzmRPhkaURC IyXEdFz2imfGPRuR0+EmYn9JP7H1uMFLPC/JKvI7QQ== X-Google-Smtp-Source: ABdhPJzWe51dgFo8YdFDbYkdUYcmO1d7+1mZzYOUd19gMk/Ayscx0kbxSccgEjton406EyAShOmFNYX5kVOyIBhDYao= X-Received: by 2002:a5d:610a:: with SMTP id v10mr19205290wrt.334.1613497465050; Tue, 16 Feb 2021 09:44:25 -0800 (PST) MIME-Version: 1.0 References: <20210202053046.1653012-1-surenb@google.com> <079db245-a08c-0dbd-01d4-8065f533652e@gmail.com> <2d303517-cdcd-9ec8-e57d-3d065edb573c@gmail.com> In-Reply-To: <2d303517-cdcd-9ec8-e57d-3d065edb573c@gmail.com> From: Suren Baghdasaryan Date: Tue, 16 Feb 2021 09:44:13 -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" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Michael, On Sat, Feb 13, 2021 at 2:04 PM Michael Kerrisk (man-pages) wrote: > > Hello Suren, > > On 2/2/21 11:12 PM, Suren Baghdasaryan wrote: > > 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. > > So, I decided to move the description of MADV_COLD and MADV_PAGEOUT > to madvise(2) and refer to that page from the process_madvise(2) > page. This avoids repeating the same information in two places. Sounds good. > > >>> 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. > > Thanks. I added a few words to clarify this. Any link where I can see the final version? > > > >> 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 for checking them. > > Cheers, > > Michael > Thanks, Suren. > > -- > Michael Kerrisk > Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ > Linux/UNIX System Programming Training: http://man7.org/training/ > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >