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 181C2C2BB48 for ; Tue, 15 Dec 2020 14:14:19 +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 BFCAE224BE for ; Tue, 15 Dec 2020 14:14:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFCAE224BE 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]:43054 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kpB5l-0002bp-N8 for qemu-devel@archiver.kernel.org; Tue, 15 Dec 2020 09:14:17 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33544) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpB2q-0008NO-0M for qemu-devel@nongnu.org; Tue, 15 Dec 2020 09:11:16 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33653) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kpB2m-0006dK-GF for qemu-devel@nongnu.org; Tue, 15 Dec 2020 09:11:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608041470; 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=kxid7UxWSQ+0Imna6OFEV9O6ID9SkP8K6TmfmOxeLJk=; b=apoTfofuasEhUvtBJkfuN61YMut3Z6cMo6kPV8pybZwCdXSaCetHeVadlKCO0xCHhveJcT l8hqgFwtRWgsKTgtzROeOJnOUGf3aTAOTjQ+lz6ZpR0supSMt7m5808z8a5QdSziQXs+J4 LIpKCW/bsbL34AY8sD4JY+gybpp1kPs= 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-177-O_BwJA_fMoW4EhydQNCmTg-1; Tue, 15 Dec 2020 09:11:09 -0500 X-MC-Unique: O_BwJA_fMoW4EhydQNCmTg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3DE941934103; Tue, 15 Dec 2020 14:11:08 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-103.ams2.redhat.com [10.36.112.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 04A5760C17; Tue, 15 Dec 2020 14:11:08 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 6F26711329A5; Tue, 15 Dec 2020 15:11:06 +0100 (CET) From: Markus Armbruster To: Eduardo Habkost Subject: Re: [PATCH v2 04/12] i386: Register feature bit properties as class properties References: <20201111183823.283752-1-ehabkost@redhat.com> <20201111183823.283752-5-ehabkost@redhat.com> Date: Tue, 15 Dec 2020 15:11:06 +0100 In-Reply-To: <20201111183823.283752-5-ehabkost@redhat.com> (Eduardo Habkost's message of "Wed, 11 Nov 2020 13:38:15 -0500") Message-ID: <87pn3b2m85.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@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_H3=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" 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. Eduardo's patch reduces run time to 0.02 seconds (40,000 allocations, 9 MiB total). It's a smaller pig now.