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 3CE3AC54764 for ; Mon, 19 Feb 2024 10:03:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rc0U2-0006cL-1S; Mon, 19 Feb 2024 05:02:46 -0500 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 1rc0Tz-0006br-Q8 for qemu-devel@nongnu.org; Mon, 19 Feb 2024 05:02:43 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rc0Tx-0001fO-WD for qemu-devel@nongnu.org; Mon, 19 Feb 2024 05:02:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1708336960; h=from:from:reply-to:reply-to:subject:subject: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=MgIfNi1yukTizBF5iD8naV/Cp7XFzo46cyMnig9W5zI=; b=UjmCLiTMmVnstqxIO+DFAAy09HusNwIxBVwj/0NtnzM00O48+AJ931uh1aQr0C41u7TWgh ixPIUmqYh1nYMV3sxWB+98ExRSED84GLYECUJwhhX9loQuwAi8wxZfTvtT02MHJuN4zchQ 5EQasnONdtEvbPEGsAuePXXkv8TKS0w= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-247-PEsoT89DOhiDPzvrOniCFQ-1; Mon, 19 Feb 2024 05:02:36 -0500 X-MC-Unique: PEsoT89DOhiDPzvrOniCFQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E4BB63C0F188; Mon, 19 Feb 2024 10:02:35 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.30]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3A2781C060AF; Mon, 19 Feb 2024 10:02:34 +0000 (UTC) Date: Mon, 19 Feb 2024 10:02:32 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Richard Henderson Cc: Alexander Monakov , qemu-devel@nongnu.org, mmromanov@ispras.ru Subject: Re: [PATCH v5 10/10] tests/bench: Add bufferiszero-bench Message-ID: References: <20240217003918.52229-1-richard.henderson@linaro.org> <20240217003918.52229-11-richard.henderson@linaro.org> <2abd887c-c99c-437c-f0bc-e06f3a13fd33@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.077, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Sat, Feb 17, 2024 at 09:21:50AM -1000, Richard Henderson wrote: > On 2/16/24 23:49, Alexander Monakov wrote: > > > > On Fri, 16 Feb 2024, Richard Henderson wrote: > > > > > Benchmark each acceleration function vs an aligned buffer of zeros. > > > > > > Signed-off-by: Richard Henderson > > > --- > > > + > > > +static void test(const void *opaque) > > > +{ > > > + size_t len = 64 * KiB; > > > > This exceeds L1 cache capacity, so the performance ceiling of L2 cache > > throughput is easier to hit with a suboptimal implementation. It also > > seems to vastly exceed typical buffer sizes in Qemu. > > > > When preparing the patch we mostly tested at 8 KiB. The size decides > > whether the branch exiting the loop becomes perfectly predictable in > > the microbenchmark, e.g. at 128 bytes per iteration it exits on the > > 63'rd iteration, which Intel predictors cannot track, so we get > > one mispredict per call. > > > > (so perhaps smaller sizes like 2 or 4 KiB are better) > > Fair. I've adjusted to loop over 1, 4, 16, 64 KiB. > > # Start of bufferiszero tests > # buffer_is_zero #0: 1KB 49227.29 MB/sec > # buffer_is_zero #0: 4KB 137461.28 MB/sec > # buffer_is_zero #0: 16KB 224220.41 MB/sec > # buffer_is_zero #0: 64KB 142461.00 MB/sec > # buffer_is_zero #1: 1KB 45423.59 MB/sec > # buffer_is_zero #1: 4KB 91409.69 MB/sec > # buffer_is_zero #1: 16KB 123819.94 MB/sec > # buffer_is_zero #1: 64KB 71173.75 MB/sec > # buffer_is_zero #2: 1KB 35465.03 MB/sec > # buffer_is_zero #2: 4KB 56110.46 MB/sec > # buffer_is_zero #2: 16KB 68852.28 MB/sec > # buffer_is_zero #2: 64KB 39043.80 MB/sec Totally nit-picking, but it would be easier to read with a little alignment and blanks lines: # buffer_is_zero #0: 1KB 49227.29 MB/sec # buffer_is_zero #0: 4KB 137461.28 MB/sec # buffer_is_zero #0: 16KB 224220.41 MB/sec # buffer_is_zero #0: 64KB 142461.00 MB/sec # buffer_is_zero #1: 1KB 45423.59 MB/sec # buffer_is_zero #1: 4KB 91409.69 MB/sec # buffer_is_zero #1: 16KB 123819.94 MB/sec # buffer_is_zero #1: 64KB 71173.75 MB/sec # buffer_is_zero #2: 1KB 35465.03 MB/sec # buffer_is_zero #2: 4KB 56110.46 MB/sec # buffer_is_zero #2: 16KB 68852.28 MB/sec # buffer_is_zero #2: 64KB 39043.80 MB/sec With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|