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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 26997C7EE2C for ; Fri, 2 Jun 2023 09:23:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q50zg-0004K0-DK; Fri, 02 Jun 2023 05:22:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q50ze-0004Jg-6c for qemu-devel@nongnu.org; Fri, 02 Jun 2023 05:22:46 -0400 Received: from mail-ed1-x52d.google.com ([2a00:1450:4864:20::52d]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1q50zc-00028M-9h for qemu-devel@nongnu.org; Fri, 02 Jun 2023 05:22:45 -0400 Received: by mail-ed1-x52d.google.com with SMTP id 4fb4d7f45d1cf-514859f3ffbso2666033a12.1 for ; Fri, 02 Jun 2023 02:22:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1685697759; x=1688289759; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=Q6wokpUFI3AgXD4Qn5C9gRNCiQYNa0dpDpjwuSa95I4=; b=xi/FlkKb+M7LlR0pDXTZxCVCSRTsvNhM17VgfSJVZcNTdYgtWjQ5XDrrz5F6Zeg6Ur CwgH8BXjz6LuHRzhRW34nf9E5jVDb4y2TNBU1UN7IqyrnJa6YsBf6vqKSBhTr2GMcYLJ pTEBVD7J9Hqi2j55Wf7i0zlV4Dfla0rhbGi+xUKWRQKG+7EivBqO1I2rVAAryk/Deqps DivLrAMUDXAftPKyGUSLK9JEYOUDz5DojcCCVZ2gQAc93IgcWxoVVjhZ3XefY37mIDf2 o0QDFDxKZoVUCMxSnK8W3RAS15hRbgu1gw80HjezEz0EJ1l+Uh33giTbfB/MKnGZtbYe uraQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685697759; x=1688289759; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Q6wokpUFI3AgXD4Qn5C9gRNCiQYNa0dpDpjwuSa95I4=; b=ZCdNMgyxiafTvIZ0xtokzaX+jB3qVBzgmdlsR+FBslNs578F3jy6PLpBZPbQlBj8x0 QhSWF7En7n25bVNmEyzSrogCNEqmKyT8fj1NInKY+ewqTM1XiOB1BnZWlulnD8NpI/Yq ydYdLms9denY8Mm1LcleJA/2ooqOazt4NJjdBGgRT/8Iy70oUlIerE0kQ3ejQqavVmqj jueC69bAdsQCxk/k476TQ/z2WDMiv8AfbdpidEZpJjQOc8u/X0e9u9MDQRpNA4xlBgLn hAE/oYuNsLYbVIK6CfPwx0fUqOQyxTCi41s2Bn3mx0SYFiTc9reZgBjh6MbeVV2iwOgk BF+A== X-Gm-Message-State: AC+VfDyOYyLYkgDKvfSPB9WgpoJCYZSVM0HoQZY9B+4jcKq/utbM/K0u uzfqAtg5v94lzsNktVYFhilB5AXYr2x0WyLYLIKtKg== X-Google-Smtp-Source: ACHHUZ7fR7tCRd0/tyEqAub7wYzB8pVRX7Nu2RrFWK4RVlIseyMXLzCv298SEnrkSIZXo9Ovh0QjbeO3zIPqBWN856g= X-Received: by 2002:aa7:df81:0:b0:514:a5f0:93c4 with SMTP id b1-20020aa7df81000000b00514a5f093c4mr1409220edy.14.1685697759192; Fri, 02 Jun 2023 02:22:39 -0700 (PDT) MIME-Version: 1.0 References: <87y1l2rixp.fsf@secure.mitica> In-Reply-To: From: Peter Maydell Date: Fri, 2 Jun 2023 10:22:28 +0100 Message-ID: Subject: Re: Big TCG slowdown when using zstd with aarch64 To: =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= Cc: Juan Quintela , qemu-devel@nongnu.org, Richard Henderson Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::52d; envelope-from=peter.maydell@linaro.org; helo=mail-ed1-x52d.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, 2 Jun 2023 at 10:10, Daniel P. Berrang=C3=A9 = wrote: > I suspect that the zstd logic takes a little bit longer in setup, > which allows often allows the guest dirty workload to get ahead of > it, resulting in a huge amount of data to transfer. Every now and > then the compression code gets ahead of the workload and thus most > data is zeros and skipped. > > IMHO this feels like just another example of compression being largely > useless. The CPU overhead of compression can't keep up with the guest > dirty workload, making the supposedly network bandwidth saving irrelevant= . It seems a bit surprising if compression can't keep up with a TCG guest workload, though... -- PMM