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=-12.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 A0CDEC07E96 for ; Thu, 8 Jul 2021 12:52:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 818AB61456 for ; Thu, 8 Jul 2021 12:52:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231725AbhGHMzQ (ORCPT ); Thu, 8 Jul 2021 08:55:16 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:40824 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230433AbhGHMzQ (ORCPT ); Thu, 8 Jul 2021 08:55:16 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 8DBF5201BF; Thu, 8 Jul 2021 12:52:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1625748753; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=TgLVJaNdKY70gVNGdPkihC8wiWwBv6Wj7xgqSR3JdnA=; b=h7aAGI5SnBVlU2zYnTj7VftfPQmVmfTdz0OfNqHb4KxKUPoGHwD7w7sNqooalRhgvQc92g rDwEDNL25kQE2WVxfMDey0/lnB97nOQwIkLZ9FFfAkfEBsZFxDFaRNsvxeYXIQozOVRNSd tb80j1SZKHkWSKXwGNlVkzQ2StySkmU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1625748753; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=TgLVJaNdKY70gVNGdPkihC8wiWwBv6Wj7xgqSR3JdnA=; b=Mea4ckys/nWDjFj0mCcHdH6zB2gOlsTJvCAKv1kWIiOkpZOBmmdL/ez88cfTVsGh7yAUJa Fh4oHguNTJxuwFBA== Received: from ds.suse.cz (ds.suse.cz [10.100.12.205]) by relay2.suse.de (Postfix) with ESMTP id 86A95A3B97; Thu, 8 Jul 2021 12:52:33 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 5F20BDAF79; Thu, 8 Jul 2021 14:49:59 +0200 (CEST) Date: Thu, 8 Jul 2021 14:49:59 +0200 From: David Sterba To: Neal Gompa Cc: David Sterba , Btrfs BTRFS Subject: Re: [PATCH 0/6] Remove highmem allocations, kmap/kunmap Message-ID: <20210708124959.GZ2610@suse.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Neal Gompa , David Sterba , Btrfs BTRFS References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, Jul 08, 2021 at 08:45:12AM -0400, Neal Gompa wrote: > On Thu, Jul 8, 2021 at 7:48 AM David Sterba wrote: > > > > The highmem was maybe was a good idea long time ago but with 64bit > > architectures everywhere I don't think we need to take it into account. > > This does not mean this 32bit won't work, just that it won't try to use > > temporary pages in highmem for compression and raid56. The key word is > > temporary. Combining a very fast device (like hundreds of megabytes > > throughput) and 32bit machine with reasonable memory (for 32bit, like > > 8G), it could become a problem once low memory is scarce. > > > > David Sterba (6): > > btrfs: drop from __GFP_HIGHMEM all allocations > > btrfs: compression: drop kmap/kunmap from lzo > > btrfs: compression: drop kmap/kunmap from zlib > > btrfs: compression: drop kmap/kunmap from zstd > > btrfs: compression: drop kmap/kunmap from generic helpers > > btrfs: check-integrity: drop kmap/kunmap for block pages > > > > fs/btrfs/check-integrity.c | 11 +++------- > > fs/btrfs/compression.c | 6 ++---- > > fs/btrfs/inode.c | 3 +-- > > fs/btrfs/lzo.c | 42 +++++++++++--------------------------- > > fs/btrfs/raid56.c | 10 ++++----- > > fs/btrfs/zlib.c | 42 +++++++++++++------------------------- > > fs/btrfs/zstd.c | 33 +++++++++++------------------- > > 7 files changed, 49 insertions(+), 98 deletions(-) > > > > I'd be concerned about the impact of this on SBC devices. All Fedora > ARM images have zstd compression applied to them, and it would suck if > we had a performance regression here because of this. How much memory do the SBC devices have?