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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A520EB64DD for ; Tue, 1 Aug 2023 09:47:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233408AbjHAJro (ORCPT ); Tue, 1 Aug 2023 05:47:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233482AbjHAJr3 (ORCPT ); Tue, 1 Aug 2023 05:47:29 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FA923A86 for ; Tue, 1 Aug 2023 02:46:04 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B30FD614BB for ; Tue, 1 Aug 2023 09:46:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BDAD9C433C7; Tue, 1 Aug 2023 09:46:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1690883163; bh=8/4yf623rSjI3i44RV1xF28lWzqnoeXZEdFcYBgm05I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0724PI9zczypy8+Pgg+cORLurQB6m23QEvZBahUluE6pIAdR/Dqx9U8IbTg6rL5ax Mg2CelXPutmPZZA644m0NtkXUTc5io4+qK+NU/s2R6FyQmCuNmKmdPqMfnWZk8ZdaM z2dsmis+b5/42AglnpfCo3I8nR7wEVQXK2Ym2GhE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hugh Dickins , Randy Dunlap , Luis Chamberlain , Christian Brauner , Andrew Morton , Sasha Levin Subject: [PATCH 6.4 138/239] tmpfs: fix Documentation of noswap and huge mount options Date: Tue, 1 Aug 2023 11:20:02 +0200 Message-ID: <20230801091930.665877363@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230801091925.659598007@linuxfoundation.org> References: <20230801091925.659598007@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Hugh Dickins [ Upstream commit 253e5df8b8f0145adb090f57c6f4e6efa52d738e ] The noswap mount option is surely not one of the three options for sizing: move its description down. The huge= mount option does not accept numeric values: those are just in an internal enum. Delete those numbers, and follow the manpage text more closely (but there's not yet any fadvise() or fcntl() which applies here). /sys/kernel/mm/transparent_hugepage/shmem_enabled is hard to describe, and barely relevant to mounting a tmpfs: just refer to transhuge.rst (while still using the words deny and force, to help as informal reminders). [rdunlap@infradead.org: fixup Docs table for huge mount options] Link: https://lkml.kernel.org/r/20230725052333.26857-1-rdunlap@infradead.org Link: https://lkml.kernel.org/r/986cb0bf-9780-354-9bb-4bf57aadbab@google.com Signed-off-by: Hugh Dickins Signed-off-by: Randy Dunlap Fixes: d0f5a85442d1 ("shmem: update documentation") Fixes: 2c6efe9cf2d7 ("shmem: add support to ignore swap") Reviewed-by: Luis Chamberlain Cc: Christian Brauner Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- Documentation/filesystems/tmpfs.rst | 47 ++++++++++++----------------- 1 file changed, 20 insertions(+), 27 deletions(-) diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst index f18f46be5c0c7..2cd8fa332feb7 100644 --- a/Documentation/filesystems/tmpfs.rst +++ b/Documentation/filesystems/tmpfs.rst @@ -84,8 +84,6 @@ nr_inodes The maximum number of inodes for this instance. The default is half of the number of your physical RAM pages, or (on a machine with highmem) the number of lowmem RAM pages, whichever is the lower. -noswap Disables swap. Remounts must respect the original settings. - By default swap is enabled. ========= ============================================================ These parameters accept a suffix k, m or g for kilo, mega and giga and @@ -99,36 +97,31 @@ mount with such options, since it allows any user with write access to use up all the memory on the machine; but enhances the scalability of that instance in a system with many CPUs making intensive use of it. +tmpfs blocks may be swapped out, when there is a shortage of memory. +tmpfs has a mount option to disable its use of swap: + +====== =========================================================== +noswap Disables swap. Remounts must respect the original settings. + By default swap is enabled. +====== =========================================================== + tmpfs also supports Transparent Huge Pages which requires a kernel configured with CONFIG_TRANSPARENT_HUGEPAGE and with huge supported for your system (has_transparent_hugepage(), which is architecture specific). The mount options for this are: -====== ============================================================ -huge=0 never: disables huge pages for the mount -huge=1 always: enables huge pages for the mount -huge=2 within_size: only allocate huge pages if the page will be - fully within i_size, also respect fadvise()/madvise() hints. -huge=3 advise: only allocate huge pages if requested with - fadvise()/madvise() -====== ============================================================ - -There is a sysfs file which you can also use to control system wide THP -configuration for all tmpfs mounts, the file is: - -/sys/kernel/mm/transparent_hugepage/shmem_enabled - -This sysfs file is placed on top of THP sysfs directory and so is registered -by THP code. It is however only used to control all tmpfs mounts with one -single knob. Since it controls all tmpfs mounts it should only be used either -for emergency or testing purposes. The values you can set for shmem_enabled are: - -== ============================================================ --1 deny: disables huge on shm_mnt and all mounts, for - emergency use --2 force: enables huge on shm_mnt and all mounts, w/o needing - option, for testing -== ============================================================ +================ ============================================================== +huge=never Do not allocate huge pages. This is the default. +huge=always Attempt to allocate huge page every time a new page is needed. +huge=within_size Only allocate huge page if it will be fully within i_size. + Also respect madvise(2) hints. +huge=advise Only allocate huge page if requested with madvise(2). +================ ============================================================== + +See also Documentation/admin-guide/mm/transhuge.rst, which describes the +sysfs file /sys/kernel/mm/transparent_hugepage/shmem_enabled: which can +be used to deny huge pages on all tmpfs mounts in an emergency, or to +force huge pages on all tmpfs mounts for testing. tmpfs has a mount option to set the NUMA memory allocation policy for all files in that instance (if CONFIG_NUMA is enabled) - which can be -- 2.40.1