From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id AB6711A074A for ; Fri, 13 Mar 2015 18:07:28 +1100 (AEDT) Message-ID: <1426230438.17565.162.camel@kernel.crashing.org> Subject: Re: [RFC] powerpc: use ticket spin lock for !CONFIG_PPC_SPLPAR From: Benjamin Herrenschmidt To: Kevin Hao Date: Fri, 13 Mar 2015 18:07:18 +1100 In-Reply-To: <20150313060913.GC24485@pek-khao-d1.corp.ad.wrs.com> References: <1426157723-28548-1-git-send-email-haokexin@gmail.com> <1426158807.17565.131.camel@kernel.crashing.org> <20150312152410.GA12372@lst.de> <20150313060913.GC24485@pek-khao-d1.corp.ad.wrs.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: Paul Mackerras , Torsten Duwe , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2015-03-13 at 14:09 +0800, Kevin Hao wrote: > On Thu, Mar 12, 2015 at 04:24:10PM +0100, Torsten Duwe wrote: > > But generally, which platforms would benefit most from this change? > > In theory, the more cpus the platform has, the more serious the thundering > herd problem is. So the latest platforms which has more cpus would benefit > most. In fact, pseries would be one to benefit ... it would be nice to find a way to sort out the lock owner problem. One idea I had was to keep the owners elsewhere, some kind of hash chain of "taken locks" hashed on the lock address. There shouldn't be *that* many locks held at a given point in time. Trying to keep the owner in a separate & non-atomic part of the lock proved being too hard due to how the lockref and generic code are interwined, though maybe somebody smarter can find a trick :-) Cheers, Ben.