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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.googlemail.com with ESMTPSA id cz6sm13912696edb.4.2022.02.01.02.51.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Feb 2022 02:51:17 -0800 (PST) Message-ID: <6b3f5a30-6f66-5aa7-293a-d6ee59487158@redhat.com> Date: Tue, 1 Feb 2022 11:51:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v3 3/3] kvm: Support for querying fd-based stats Content-Language: en-US To: Mark Kanda , qemu-devel@nongnu.org References: <20220131194312.1192626-1-mark.kanda@oracle.com> <20220131194312.1192626-4-mark.kanda@oracle.com> From: Paolo Bonzini In-Reply-To: <20220131194312.1192626-4-mark.kanda@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::533 (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::533; envelope-from=paolo.bonzini@gmail.com; helo=mail-ed1-x533.google.com X-Spam_score_int: -6 X-Spam_score: -0.7 X-Spam_bar: / X-Spam_report: (-0.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.248, NICE_REPLY_A=-0.001, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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: , Cc: berrange@redhat.com, armbru@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/31/22 20:43, Mark Kanda wrote: > > + for (i = 0; i < header->num_desc; ++i) { > + struct kvm_stats_desc *pdesc = (void *)stats_desc + i * size_desc; > + size_data = pdesc->size * sizeof(uint64_t); > + > + uint64_t *stats_data = g_malloc(size_data); > + > + ret = pread(stats_fd, stats_data, size_data, > + header->data_offset + pdesc->offset); How hard would it be to cache the descriptors? Ideally, a query-stats command would do only one pread. Paolo