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 16A06C77B7C for ; Tue, 18 Apr 2023 21:20:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232635AbjDRVUO (ORCPT ); Tue, 18 Apr 2023 17:20:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231171AbjDRVUL (ORCPT ); Tue, 18 Apr 2023 17:20:11 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0834903B for ; Tue, 18 Apr 2023 14:20:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3Km/vnh/sBC4DQYO69Q00ljyDReo/R1BeGSdOPULOKw=; b=1L14NJ+lXlSRxbmu5FayimPVss bavZ6XsrainBIv/5bbMp3rBuUpTS3nQl+23Ul819ig5kO7uZAjLFcxDNOL0tNvLePvbwUuCG3pPTR 4b1IIK8sejumG/QXJ1HuwBqTUUV/NaxX/YGGbqDkbk0zRph/UfJ6IlC8kk9s4IZE5fTfrdlTponOK qOX7dWJyeft5qvMgd1rlX2Npl/Y0nyX4gWgL2NZo56NopoNeGgdfOVJQzHFpwbx/dFYbYGuh+tp7Z FbccCeJ2adPHUoMzGKF4bY/db598SuCcpN0MslTePYUdyT+VFw/8RbXQEQJiKsWikTVsJ89d/IDLS h1pGV9KQ==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1posk5-003MpZ-21; Tue, 18 Apr 2023 21:20:01 +0000 Date: Tue, 18 Apr 2023 14:20:01 -0700 From: Luis Chamberlain To: Hugh Dickins Cc: akpm@linux-foundation.org, willy@infradead.org, brauner@kernel.org, linux-mm@kvack.org, p.raghav@samsung.com, da.gomez@samsung.com, a.manzanares@samsung.com, dave@stgolabs.net, yosryahmed@google.com, keescook@chromium.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org, David Hildenbrand Subject: Re: [PATCH v2 5/6] shmem: update documentation Message-ID: References: <20230309230545.2930737-1-mcgrof@kernel.org> <20230309230545.2930737-6-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Luis Chamberlain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 17, 2023 at 10:29:59PM -0700, Hugh Dickins wrote: > On Thu, 9 Mar 2023, Luis Chamberlain wrote: > > > Update the docs to reflect a bit better why some folks prefer tmpfs > > over ramfs and clarify a bit more about the difference between brd > > ramdisks. > > > > While at it, add THP docs for tmpfs, both the mount options and the > > sysfs file. > > Okay: the original canonical reference for THP options on tmpfs has > been Documentation/admin-guide/mm/transhuge.rst. You're right that > they would be helpful here too: IIRC (but I might well be confusing > with our Google tree) we used to have them documented in both places, > but grew tired of keeping the two in synch. You're volunteering to > do so! so please check now that they tell the same story. Hehe. Sure, we should just make one point to the other. Which one should be the authoritive source? > But nowadays, "man 5 tmpfs" is much more important (and that might > give you a hint for what needs to be done after this series goes into > 6.4-rc - and I wonder if there are tmpfs manpage updates needed from > Christian for idmapped too? or already taken care of?). Sure, what's the man page git tree to use? I can do that once these documents are settled as well. I'll send fixes. > There's a little detail we do need you to remove, indicated below. > > > +====== ============================================================ > > +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() > > You're taking the source too literally there. Minor point is that there > is no fadvise() for this, to date anyway. Major point is: have you tried > mounting tmpfs with huge=0 etc? I did propose "huge=0" and "huge=1" years > ago, but those "never" went in, it's "always" been the named options. > Please remove those misleading numbers, it's "huge=never" etc. Will do. > > +== ============================================================ > > +-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 > > Likewise here, please delete the invalid "-1" and "-2" notations, > -1 and -2 are just #defines for use in the kernel source. ok! > And the description above is not quite accurate: it is very hard to > describe shmem_enabled, partly because it combines two different things. > It's partly the "huge=" mount option for any "internal mount", those > things like SysV SHM and memfd and i915 and shared-anonymous: the shmem > which has no user-visible mount to hold the option. But also these > "deny" and "force" overrides affecting *all* internal and visible mounts. I see thanks. Luis