From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755010AbbFKPC7 (ORCPT ); Thu, 11 Jun 2015 11:02:59 -0400 Received: from mail-wg0-f48.google.com ([74.125.82.48]:32781 "EHLO mail-wg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752771AbbFKPC5 (ORCPT ); Thu, 11 Jun 2015 11:02:57 -0400 Date: Thu, 11 Jun 2015 17:02:51 +0200 From: Ingo Molnar To: Mel Gorman Cc: Andrew Morton , Rik van Riel , Hugh Dickins , Minchan Kim , Dave Hansen , Andi Kleen , H Peter Anvin , Linus Torvalds , Thomas Gleixner , Peter Zijlstra , Linux-MM , LKML Subject: Re: [PATCH 2/4] mm: Send one IPI per CPU to TLB flush all entries after unmapping pages Message-ID: <20150611150250.GA14086@gmail.com> References: <1433871118-15207-1-git-send-email-mgorman@suse.de> <1433871118-15207-3-git-send-email-mgorman@suse.de> <20150610083332.GA25605@gmail.com> <20150610085950.GB26425@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150610085950.GB26425@suse.de> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mel Gorman wrote: > > In the full-flushing case (v6 without patch 4) the batching limit is > > 'infinite', we'll batch as long as possible, right? > > No because we must flush before pages are freed so the maximum batching is > related to SWAP_CLUSTER_MAX. If we free a page before the flush then in theory > the page can be reallocated and a stale TLB entry can allow access to unrelated > data. It would be almost impossible to trigger corruption this way but it's a > concern. Well, could we say double SWAP_CLUSTER_MAX to further reduce the IPI rate? Thanks, Ingo