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 E24DBEB64D9 for ; Sat, 17 Jun 2023 23:01:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qAeuq-0002Jv-4j; Sat, 17 Jun 2023 19:01:08 -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 1qAeuj-0002I5-PY for qemu-devel@nongnu.org; Sat, 17 Jun 2023 19:01:02 -0400 Received: from mail-ej1-x62a.google.com ([2a00:1450:4864:20::62a]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qAeuh-0006qu-W6 for qemu-devel@nongnu.org; Sat, 17 Jun 2023 19:01:01 -0400 Received: by mail-ej1-x62a.google.com with SMTP id a640c23a62f3a-9827bd8e0afso333445966b.1 for ; Sat, 17 Jun 2023 16:00:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1687042857; x=1689634857; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=cy27xGiAcRXfgBmx++aR1JaCOJvCFkxE3gynhdtYCfc=; b=PrG7Bi3XBvpMlIq5QBnkdgX6R1hmIJjyrlJriZfoJ7++qaFzyFGyQ9hNeVGX1CKCOU qgcheExMvAzDLmMbjZ/FbDcjAsSusjObfZdvlVT04QkiaJQP89AoUgPCyybWc88owhKN 0HA+aRZudasXIUV2m73BQPdj3Pi8Z3QuSKh+afq71jnNUNjq94jYaaGGlcNoASP0RrjL wse1hRD3YDXbALsI1AQintkZrOZxgF7J47eApZxZj5U6jYIFcDzEkxJM3xJu+HHt0d3/ HuRVL8yv/cUKOQjYRBL8JapV4/xscui1uzzhNevWE/msh4GJ1pJmz94QvMn7tXGR+yDx wC2w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687042857; x=1689634857; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=cy27xGiAcRXfgBmx++aR1JaCOJvCFkxE3gynhdtYCfc=; b=c0h4n3UzPFKAZ2UlikR5l6DdDEuuK1LlYv6EAqxZ1J97GdvwOzBfPAW6OkCnRukD2a UZILIbX8MO5sJb2+e0lJv/0RIb7aqHthGZomiB1Da99VSizAN6T/BeXy1+ouWw+qfSFL lNp5B47G1+EpPBLt6JvwLsfu7J0rA3h8zvr/cUKuL7Hu6fCoyee0XX85efkEaU/ABsMT AyrGbxxgB6rYMy/DGALc2CxzG6zhEV+BvvXqXi+KjhqtmY4k7yPIOiyTKyxoS/pyVJ0G KysWrdWJN7QCj1C5qUmVuyYvxaqEI4eS+1C0pfW9jviyUkSDrCbkcBf0QHPPfirTOw2O qTiQ== X-Gm-Message-State: AC+VfDyVerDBxmna5pHAWL1Zt9yYkAQLnw/NbhIiMa8ghPjSnt/jdXmW 1U6aB4/97ccuu12ajjyOqSK/Cw== X-Google-Smtp-Source: ACHHUZ4+KKaB4KOO7YWhTgg76gHBaX0eo6R9EPi+m7re2GMxmcyiajmNTgjZ6YM/9EfPOSQghK8AbA== X-Received: by 2002:a17:907:7e9f:b0:988:7ccc:3e11 with SMTP id qb31-20020a1709077e9f00b009887ccc3e11mr72762ejc.24.1687042856872; Sat, 17 Jun 2023 16:00:56 -0700 (PDT) Received: from [192.168.69.115] ([176.176.141.220]) by smtp.gmail.com with ESMTPSA id v18-20020a5d43d2000000b0030ae93bd196sm27212824wrr.21.2023.06.17.16.00.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 17 Jun 2023 16:00:56 -0700 (PDT) Message-ID: Date: Sun, 18 Jun 2023 01:00:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.11.2 Subject: Re: [PATCH v2] kvm: reuse per-vcpu stats fd to avoid vcpu interruption Content-Language: en-US To: Marcelo Tosatti , Markus Armbruster Cc: qemu-devel , Paolo Bonzini , Mark Kanda References: <87h6rab8gv.fsf@pond.sub.org> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::62a; envelope-from=philmd@linaro.org; helo=mail-ej1-x62a.google.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.091, 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 Hi Marcelo, On 16/6/23 19:44, Marcelo Tosatti wrote: > > A regression has been detected in latency testing of KVM guests. > More specifically, it was observed that the cyclictest > numbers inside of an isolated vcpu (running on isolated pcpu) are: > > # Max Latencies: 00090 00096 00141 > > Where a maximum of 50us is acceptable. > > The implementation of KVM_GET_STATS_FD uses run_on_cpu to query > per vcpu statistics, which interrupts the vcpu (and is unnecessary). > > To fix this, open the per vcpu stats fd on vcpu initialization, > and read from that fd from QEMU's main thread. > > Signed-off-by: Marcelo Tosatti > static void query_stats(StatsResultList **result, StatsTarget target, > - strList *names, int stats_fd, Error **errp) > + strList *names, int stats_fd, CPUState *cpu, > + Error **errp) > { > struct kvm_stats_desc *kvm_stats_desc; > struct kvm_stats_header *kvm_stats_header; > @@ -4096,7 +4099,7 @@ static void query_stats(StatsResultList **result, StatsTarget target, > break; > case STATS_TARGET_VCPU: > add_stats_entry(result, STATS_PROVIDER_KVM, > - current_cpu->parent_obj.canonical_path, > + cpu->parent_obj.canonical_path, Can we get a NULL deref here ... > stats_list); > break; > default: > static void query_stats_cb(StatsResultList **result, StatsTarget target, > @@ -4180,7 +4180,7 @@ static void query_stats_cb(StatsResultList **result, StatsTarget target, > error_setg_errno(errp, errno, "KVM stats: ioctl failed"); > return; > } > - query_stats(result, target, names, stats_fd, errp); > + query_stats(result, target, names, stats_fd, NULL, errp); ... from here? > close(stats_fd); > break; > }