From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 35595 invoked by alias); 31 May 2019 02:48:24 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 35564 invoked by uid 89); 31 May 2019 02:48:18 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-6.3 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS autolearn=ham version=3.3.1 spammy=HX-Languages-Length:1092, locked X-HELO: gateway30.websitewelcome.com Received: from gateway30.websitewelcome.com (HELO gateway30.websitewelcome.com) (192.185.144.21) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Fri, 31 May 2019 02:48:17 +0000 Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway30.websitewelcome.com (Postfix) with ESMTP id E75E2F33 for ; Thu, 30 May 2019 21:48:07 -0500 (CDT) Received: from box5379.bluehost.com ([162.241.216.53]) by cmsmtp with SMTP id WXaRhr6V1YTGMWXaRhqGh5; Thu, 30 May 2019 21:48:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tromey.com; s=default; h=Content-Type:MIME-Version:Message-ID:In-Reply-To:Date: References:Subject:Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=nfbo5mjt4aVbzJXXaav58ueFnxD+M+IFPm0kEi3GKRE=; b=VD+KXHPCJE32DFAu+ag3G6ZKqI QnKlgNHqUMFBp6skyS2Yjqrcwtj4S11DBP5gNT3h1Tixe9v+npJvmB58FB5tLSJcMh4FwpWb5KPBm aN5Aa8Q7MxVxSXWv5GXmMnRYV; Received: from 174-29-48-168.hlrn.qwest.net ([174.29.48.168]:38816 helo=bapiya) by box5379.bluehost.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1hWXaR-002Mnn-Kl; Thu, 30 May 2019 21:48:07 -0500 From: Tom Tromey To: Tom Tromey Cc: Philippe Waroquiers , gdb-patches@sourceware.org Subject: Re: [PATCH v2 0/8] Demangle minimal symbol names in worker threads References: <20190518210010.27697-1-tom@tromey.com> <1558274338.1454.13.camel@skynet.be> <87a7figtpz.fsf@tromey.com> Date: Fri, 31 May 2019 02:48:00 -0000 In-Reply-To: <87a7figtpz.fsf@tromey.com> (Tom Tromey's message of "Sun, 19 May 2019 12:55:04 -0600") Message-ID: <87sgsvcpax.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1.91 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-SW-Source: 2019-05/txt/msg00739.txt.bz2 Tom> Locally I only saw utilization of 1.5 CPUs or so -- so, not very Tom> parallel yet. I found the "mutrace" tool and it looks like the new mutex is heavily contended. This is pretty much what I suspected, but still unfortunate. $ mutrace -d ./gdb -nx -batch ./gdb [...] Mutex # Locked Changed Cont. tot.Time[ms] avg.Time[ms] max.Time[ms] Flags 2 3714780 45723 26425 975.514 0.000 22.141 M-.--. I'm not really sure what to do about it. I do wonder if there are many duplicates when demangling minsym names. One idea would be to demangle in parallel and only then fill in the table. A similar problem will occur when/if we want to parallelize psymbol reading. Those use the demangle hash table, but also the bcache. (The bcache is important, but I found recently that the demangling isn't really needed -- the names are demangled due to the physname work, and the demangle hash table is only used to ensure that the bcache gives good results. Removing the demangling step here can also provide a nice speedup...) Tom