From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52945) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fWkQK-0008AX-3W for qemu-devel@nongnu.org; Sat, 23 Jun 2018 11:26:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fWkQH-0002KQ-0J for qemu-devel@nongnu.org; Sat, 23 Jun 2018 11:26:00 -0400 Received: from mail-pg0-x242.google.com ([2607:f8b0:400e:c05::242]:38959) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1fWkQG-0002K6-PP for qemu-devel@nongnu.org; Sat, 23 Jun 2018 11:25:56 -0400 Received: by mail-pg0-x242.google.com with SMTP id n2-v6so794607pgq.6 for ; Sat, 23 Jun 2018 08:25:56 -0700 (PDT) References: <20180621173635.21537-1-richard.henderson@linaro.org> <20180622211244.GA11346@flamenco> From: Richard Henderson Message-ID: <1319a0f0-0009-ebfc-dab4-eec196ba8ba5@linaro.org> Date: Sat, 23 Jun 2018 08:25:52 -0700 MIME-Version: 1.0 In-Reply-To: <20180622211244.GA11346@flamenco> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 0/2] linux-user: Change mmap_lock to rwlock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Emilio G. Cota" Cc: qemu-devel@nongnu.org, laurent@vivier.eu, qemu-arm@nongnu.org On 06/22/2018 02:12 PM, Emilio G. Cota wrote: > I'm curious to see how much perf could be gained. It seems that the hold > times in SVE code for readers might not be very large, which > then wouldn't let us amortize the atomic inc of the read lock > (IOW, we might not see much of a difference compared to a regular > mutex). In theory, the uncontended case for rwlocks is the same as a mutex. > Are you using any benchmark that shows any perf difference? Not so far. Glibc has some microbenchmarks for strings, which I will try next week, but they are not multi-threaded. Maybe just run 4 threads of those benchmark? r~