From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 81AE91F453 for ; Fri, 18 Jan 2019 21:41:24 +0000 (UTC) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:references:date:in-reply-to :message-id:mime-version:content-type; q=dns; s=default; b=xzYQq f0VY/lZc0FjxuqDc0Kw2X9fYx725ZnwrVZJ48zMPmSX+DRn/cKmI3Yz8hd7uRQ5A IpJ4jNnOyMYsfuOpdwnfP9NBn+ipN4jALZ3dToBGTZ94TWLt1gGHEcv5jQCJ5XdW k/olFXNhztOrhqETZgjbnwpvi7yi1+2EPPAmdo= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:references:date:in-reply-to :message-id:mime-version:content-type; s=default; bh=IaWu1j62an2 fP9/oscPa7QNoUew=; b=Lq68JyL/oKq56DGU/lEqz4Pg/IKbU3MN6pFN10jyPLS PkxQQ0Cllonu6oTbGuYHuHiDJx/7dZfrJkrxM6KtX0lqK3TxJnaAl3tuRECXHjLu vUp1sBpuO66uqHjNwxzshjUyWOdVoTvu+ZQTcuQjP5DI30t9c+Q0Qc6v4M6weFZ8 = Received: (qmail 98189 invoked by alias); 18 Jan 2019 21:41:21 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 98178 invoked by uid 89); 18 Jan 2019 21:41:21 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: mx1.redhat.com From: Florian Weimer To: Siddhesh Poyarekar Cc: Carlos O'Donell , libc-alpha@sourceware.org Subject: Re: [PATCH] malloc: Revert fastbins to old-style atomics References: <87d0owzrcf.fsf@oldenburg2.str.redhat.com> <793fa38d-e8aa-4903-5dfd-7997d511c367@redhat.com> <87k1j4wrbk.fsf@oldenburg2.str.redhat.com> <87zhrynot6.fsf@oldenburg2.str.redhat.com> <959cf579-3c31-34f1-c791-6a9319700fb2@gotplt.org> Date: Fri, 18 Jan 2019 22:41:13 +0100 In-Reply-To: <959cf579-3c31-34f1-c791-6a9319700fb2@gotplt.org> (Siddhesh Poyarekar's message of "Sat, 19 Jan 2019 00:09:48 +0530") Message-ID: <87h8e5k5ja.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain * Siddhesh Poyarekar: > On 18/01/19 5:46 PM, Florian Weimer wrote: >> Siddhesh, is this okay to commit before the release? > > This is OK. +1 on putting the patch back in once master reopens and get > architecture maintainers to do an RCA. I've pushed the revert. I looked at this some more (including the POWER disassembly), and I think the old code approximates what would happen with memory_order_consume (if we had a working implementation of that) and exploits the data dependency detection in the CPU to reduce the need for barriers. Thanks, Florian