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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,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 16F5FC2BB48 for ; Tue, 15 Dec 2020 15:02:55 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 7D8032255F for ; Tue, 15 Dec 2020 15:02:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D8032255F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52948 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kpBqn-00030N-A0 for qemu-devel@archiver.kernel.org; Tue, 15 Dec 2020 10:02:53 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:46336) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpBpk-0002ER-OP for qemu-devel@nongnu.org; Tue, 15 Dec 2020 10:01:48 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:45684) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kpBph-0007N8-7B for qemu-devel@nongnu.org; Tue, 15 Dec 2020 10:01:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608044503; h=from:from: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=wYImjP3jUPfcdebbMrN6W9rsRHv2FDZkYNLmuTkX4pQ=; b=Gahg/c35kpdt6pPk2oI7OQEl7YyP62JF6ASnBeKFU/xN67rH98OXq+z/Ajw91p9FJzBRUl fdSiMidNF0ExnIulScG1t4HtWJDqHlEEWAqXss/+KThwxgN0Z/9m6k8XpGvmag4uHE5tMn 8OVmxk8QtmWeou/EftI4eeA1qx3drkg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-456-c-GUBfN2NfaR5aN5gVg25g-1; Tue, 15 Dec 2020 10:01:41 -0500 X-MC-Unique: c-GUBfN2NfaR5aN5gVg25g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E45721E7E6; Tue, 15 Dec 2020 15:01:19 +0000 (UTC) Received: from localhost (ovpn-115-226.rdu2.redhat.com [10.10.115.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id 50EF374ADC; Tue, 15 Dec 2020 15:01:19 +0000 (UTC) Date: Tue, 15 Dec 2020 10:01:18 -0500 From: Eduardo Habkost To: Markus Armbruster Subject: Re: [PATCH v2 04/12] i386: Register feature bit properties as class properties Message-ID: <20201215150118.GU1289986@habkost.net> References: <20201111183823.283752-1-ehabkost@redhat.com> <20201111183823.283752-5-ehabkost@redhat.com> <87pn3b2m85.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87pn3b2m85.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-124.mimecast.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, DKIMWL_WL_HIGH=-0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Daniel P. Berrange" , Paolo Bonzini , John Snow , qemu-devel@nongnu.org, Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Dec 15, 2020 at 03:11:06PM +0100, Markus Armbruster wrote: > Eduardo Habkost writes: > > > Class properties make QOM introspection simpler and easier, as > > they don't require an object to be instantiated. > > > > Signed-off-by: Eduardo Habkost > > This is significantly more than just "simpler and easier". > > The other day, I played with the QMP core to reduce its appetite for > malloc. I came up with patches that should approximately halve it, and > felt quite pleased with myself. I looked for a simple test to > demonstrate the effect. Something with plenty of output. Hmm, why not > query-cpu-definitions, it produces about 32KiB. Instrument, instrument, > run, ... whaaaat?!? > > My patches save some 7000 allocations (670 KiB total), roughly matching > my expectations. > > Turns out this is a drop in the bucket: query-cpu-definitions still > takes some 180,000 allocations (almost 12 MiB total). They're hiding > behind this line in qmp_query_cpu_definitions(): > > g_slist_foreach(list, x86_cpu_definition_entry, &cpu_list); > > The line takes more than a quarter second for me. > > Hogging the main loop for a quarter second is not good. Wow! > > Eduardo's patch reduces run time to 0.02 seconds (40,000 allocations, 9 > MiB total). It's a smaller pig now. Thanks for investigating this! I'll amend the commit message with: Also, the hundreds of instance properties were having an impact on QMP commands that create temporary CPU objects. On my machine, run time of qmp_query_cpu_definitions() patch changed from ~200ms to ~16ms after applying this patch. Numbers were obtained with: $ sudo perf probe -v -x ./qemu-system-x86_64 -a 'qmp_query_cpu_definitions%return' -a 'qmp_query_cpu_definitions' $ echo -e '{"execute": "qmp_capabilities"}\n{"execute": "query-cpu-definitions"}\n{"execute": "quit"}' | sudo perf trace -e 'probe_qemu:*' ./qemu-system-x86_64 -S -display none -qmp stdio > /dev/null Before: 0.000 qemu-system-x8/3103211 probe_qemu:qmp_query_cpu_definitions(__probe_ip: 94851767056275) 204.072 qemu-system-x8/3103211 probe_qemu:qmp_query_cpu_definitions__return(__probe_func: 94851767056275, __probe_ret_ip: 94851768499362) After: 0.000 qemu-system-x8/3105969 probe_qemu:qmp_query_cpu_definitions(__probe_ip: 94554723186579) 16.445 qemu-system-x8/3105969 probe_qemu:qmp_query_cpu_definitions__return(__probe_func: 94554723186579, __probe_ret_ip: 94554724629631) -- Eduardo