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To: Owen Anderson References: <7c416109-6431-076e-2284-0f8406931ab9@linaro.org> From: Richard Henderson Message-ID: <942d4ac4-e624-11f6-f3c8-28d64ab568d5@linaro.org> Date: Mon, 19 Oct 2020 15:58:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::444; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x444.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: Paolo Bonzini , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 10/19/20 3:44 PM, Owen Anderson wrote: > My use case is currently using QEMU 4.0, but we will be moving to QEMU > 4.2 soon. I do not have --enable-tcg-debug enabled. > e979972a6a1 does look promising, and like it might deliver increased > performance for our use case. It looks like the code in 4.0 is doing a > lot more work gathering the flags values from a variety of places. Yes, before 4.2, we did a *lot* more work gathering flags, and the overhead you see roughly corresponds with what I saw. r~