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 9D212C43217 for ; Sat, 16 Apr 2022 02:20:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229884AbiDPCWq (ORCPT ); Fri, 15 Apr 2022 22:22:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229769AbiDPCWT (ORCPT ); Fri, 15 Apr 2022 22:22:19 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1439C58E75; Fri, 15 Apr 2022 19:19:49 -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=ZM3lfs/b3lAESP5zz9nLnOwj5qAuBZLAI/rah4e2ykc=; b=H4gURL8nIMUmE4/AHGNEwndQpZ NhOsASQcw8Lf8fWI3xWKAh8K2mecRE3TlV41+ua+9MCy+wgYxN0tBPBaP5mFbUl+UGiUZ3hTYz6xK 4gmxUjA11Pv2NOoPAsxowiJPNXRwP9nxJKbOXAkMTazILTit3v9CrWfn/AV7oPdsoEWijZJcm9++0 BG56SlV78tDkfVdhZXD84QVKIcljHBv25fYECsMMmuKd6vL0/y0T+lZ/UWkTtf4PmDiWRAPZK1Cv5 F4rUu6rEHY8ctjs6b4JGjDj7IT5+nGd9R8UwgdPbhBGXRAJyCtMB29Cp4kVRV5SVvauy6NNLBGlGc ll1zE/Gg==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nfXSu-00BuX1-Sd; Sat, 16 Apr 2022 01:43:09 +0000 Date: Fri, 15 Apr 2022 18:43:08 -0700 From: Luis Chamberlain To: Song Liu , Linus Torvalds Cc: bpf , Linux-MM , open list , Alexei Starovoitov , Daniel Borkmann , Kernel Team , Andrew Morton , "Edgecombe, Rick P" , Christoph Hellwig , imbrenda@linux.ibm.com Subject: Re: [PATCH v4 bpf 0/4] vmalloc: bpf: introduce VM_ALLOW_HUGE_VMAP Message-ID: References: <20220415164413.2727220-1-song@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 Fri, Apr 15, 2022 at 06:42:27PM -0700, Luis Chamberlain wrote: > On Fri, Apr 15, 2022 at 06:34:16PM -0700, Song Liu wrote: > > On Fri, Apr 15, 2022 at 12:05 PM Luis Chamberlain wrote: > > > > > > On Fri, Apr 15, 2022 at 09:44:09AM -0700, Song Liu wrote: > > > > Changes v3 => v4: > > > > 1. Fix __weak module_alloc_huge; remove unused vmalloc_huge; rename > > > > __vmalloc_huge => vmalloc_huge. (Christoph Hellwig) > > > > 2. Use vzalloc (as it was before vmalloc_no_huge) and clean up comments in > > > > kvm_s390_pv_alloc_vm. > > > > > > > > Changes v2 => v3: > > > > 1. Use __vmalloc_huge in alloc_large_system_hash. > > > > 2. Use EXPORT_SYMBOL_GPL for new functions. (Christoph Hellwig) > > > > 3. Add more description about the issues and changes.(Christoph Hellwig, > > > > Rick Edgecombe). > > > > > > > > Changes v1 => v2: > > > > 1. Add vmalloc_huge(). (Christoph Hellwig) > > > > 2. Add module_alloc_huge(). (Christoph Hellwig) > > > > 3. Add Fixes tag and Link tag. (Thorsten Leemhuis) > > > > > > > > Enabling HAVE_ARCH_HUGE_VMALLOC on x86_64 and use it for bpf_prog_pack has > > > > caused some issues [1], as many users of vmalloc are not yet ready to > > > > handle huge pages. To enable a more smooth transition to use huge page > > > > backed vmalloc memory, this set replaces VM_NO_HUGE_VMAP flag with an new > > > > opt-in flag, VM_ALLOW_HUGE_VMAP. More discussions about this topic can be > > > > found at [2]. > > > > > > > > Patch 1 removes VM_NO_HUGE_VMAP and adds VM_ALLOW_HUGE_VMAP. > > > > Patch 2 uses VM_ALLOW_HUGE_VMAP in bpf_prog_pack. > > > > > > > > [1] https://lore.kernel.org/lkml/20220204185742.271030-1-song@kernel.org/ > > > > [2] https://lore.kernel.org/linux-mm/20220330225642.1163897-1-song@kernel.org/ > > > > > > Looks good except for that I think this should just wait for v5.19. The > > > fixes are so large I can't see why this needs to be rushed in other than > > > the first assumptions of the optimizations had some flaws addressed here. > > > > We need these changes to fix issues like [3]. Note that there might > > still be some > > undiscovered issues with huge page backed vmalloc memory on powerpc, which > > had HAVE_ARCH_HUGE_VMALLOC enabled since the 5.15 kernel. As we > > agreed, the new opt-in flag is a safer approach here. We probably should have > > 1/4 and 2/4 back ported to stable. Therefore, I think shipping this > > set now would > > give us a more reliable 5.18 release. > > > > Does this make sense? > > Yes absolutely, but that sounds like that optimization should just be > reverted completely from v5.18 isntead then no? Or if one can skip the > optimizations for v5.18 with a small patch, and then enable for v5.19. In any case it is up to Linus, I already chimed in with my opinion. Luis