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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 98379C64EB1 for ; Thu, 6 Dec 2018 15:47:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D828214C1 for ; Thu, 6 Dec 2018 15:47:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=oberhumer.com header.i=@oberhumer.com header.b="AvIX82gQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D828214C1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=oberhumer.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726181AbeLFPre (ORCPT ); Thu, 6 Dec 2018 10:47:34 -0500 Received: from mail.servus.at ([193.170.194.20]:49372 "EHLO mail.servus.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725871AbeLFPrd (ORCPT ); Thu, 6 Dec 2018 10:47:33 -0500 Received: from localhost (localhost [127.0.0.1]) by mail.servus.at (Postfix) with ESMTP id B69BF3000694; Thu, 6 Dec 2018 16:47:31 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=oberhumer.com; h= content-transfer-encoding:content-type:content-type:in-reply-to :mime-version:user-agent:date:date:message-id:organization:from :from:references:subject:subject:received:received; s=main; t= 1544111246; x=1545925647; bh=kltSlKA3mbcTujRIdGfrANs0ZeALK2B9AEr AOYNpXsA=; b=AvIX82gQyQoo6zR6Hn1mM2z9MSE2T1E8X1Bip2hnWLtlujX9AFt e/viIiv2WeHITA/VzcSeaXOnHLN8qATiCmapH2SotFkZktthnsmlG5ydRlzVzSTR ppfxFPx3v1xTbarRdQa3Eqj2GSqZRy/TRfioPMImGZEYtceS+eYLFzKk= X-Virus-Scanned: amavisd-new at servus.at Received: from mail.servus.at ([127.0.0.1]) by localhost (mail.servus.at [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6MxphbQIXpG4; Thu, 6 Dec 2018 16:47:26 +0100 (CET) Received: from [192.168.216.53] (unknown [81.10.228.128]) (Authenticated sender: oh_markus) by mail.servus.at (Postfix) with ESMTPSA id A70973000692; Thu, 6 Dec 2018 16:47:25 +0100 (CET) Subject: Re: [PATCH v4 0/7] lib/lzo: performance improvements To: Dave Rodgman , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" References: <20181130142600.13782-1-dave.rodgman@arm.com> Cc: "herbert@gondor.apana.org.au" , "davem@davemloft.net" , Matt Sealey , "nitingupta910@gmail.com" , "minchan@kernel.org" , "sergey.senozhatsky.work@gmail.com" , "sonnyrao@google.com" , "gregkh@linuxfoundation.org" , nd , "sfr@canb.auug.org.au" From: "Markus F.X.J. Oberhumer" Organization: oberhumer.com Message-ID: <5C09448C.8010506@oberhumer.com> Date: Thu, 6 Dec 2018 16:47:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20181130142600.13782-1-dave.rodgman@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-11-30 15:26, Dave Rodgman wrote: > This patch series introduces performance improvements for lzo. > > The previous version of this patchset is here: > https://lkml.org/lkml/2018/11/30/807 > > This version of the patchset fixes a maybe-used-uninitialized warning > (although the previous version was still safe). > > Dave Hi Dave, as indicated in my previous mail please split your series into three distinct pull requests. Request 1 - ARM64 improvements; acked by me [PATCH 1/8] lib/lzo: tidy-up ifdefs [PATCH 3/8] lib/lzo: enable 64-bit CTZ on Arm [PATCH 4/8] lib/lzo: 64-bit CTZ on arm64 [PATCH 5/8] lib/lzo: fast 8-byte copy on arm64 are simple arch patches that give a nice speedup on ARM64 and should get merged ASAP. Request 2 - add COPY16; *NOT* acked by me [PATCH 2/8] lib/lzo: clean-up by introducing COPY16 is still not correct because of possible overlapping copies. I'll address this on the weekend. Request 3 - add lzo-rle; *NOT* acked by me [PATCH 6/8] lib/lzo: implement run-length encoding [PATCH 7/8] lib/lzo: separate lzo-rle from lzo [PATCH 8/8] zram: default to lzo-rle instead of lzo This can *NOT* be applied in the current implementation. It (1) silently changes the compressed data format, (2) crashes on MIPS, and (3) makes compression and decompression on typical data 10% slower on X86_64 with our internal benchmarks, and (4) has to be carefully checked for buffer overflows. I understand that we want some optimizations for data with many zeros like in the typical ZRAM use case, but the implementation will clearly need some more work. I'll also have a look at the weekend - eg I have a nice idea how to deal with (1). As a final comment, I question the quality your benchmarks - combining arch-related ARM64 improvements and algorithmic changes into one benchmark comparision is just unprofessional marketing. Cheers, Markus -- Markus Oberhumer, , http://www.oberhumer.com/