From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932260AbaFCN22 (ORCPT ); Tue, 3 Jun 2014 09:28:28 -0400 Received: from mail-la0-f41.google.com ([209.85.215.41]:51443 "EHLO mail-la0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753512AbaFCN20 (ORCPT ); Tue, 3 Jun 2014 09:28:26 -0400 From: Rasmus Villemoes To: Minchan Kim Cc: Dave Chinner , Linus Torvalds , Linux Kernel Mailing List , Andrew Morton , linux-mm , "H. Peter Anvin" , Ingo Molnar , Peter Zijlstra , Mel Gorman , Rik van Riel , Johannes Weiner , Hugh Dickins , Rusty Russell , "Michael S. Tsirkin" , Dave Hansen , Steven Rostedt Subject: Re: [RFC 2/2] x86_64: expand kernel stack to 16K Organization: D03 References: <1401260039-18189-1-git-send-email-minchan@kernel.org> <1401260039-18189-2-git-send-email-minchan@kernel.org> <20140528223142.GO8554@dastard> <20140529013007.GF6677@dastard> <20140529015830.GG6677@dastard> <20140529233638.GJ10092@bbox> <20140530001558.GB14410@dastard> <20140530021247.GR10092@bbox> X-Hashcash: 1:20:140603:linux-mm@kvack.org::vv19OTxOB+80FfgE:00000000000000000000000000000000000000000000cUD X-Hashcash: 1:20:140603:david@fromorbit.com::2fxQO9YsgV9AcOa7:0000000000000000000000000000000000000000000IcL X-Hashcash: 1:20:140603:minchan@kernel.org::onVjjUcRkHDNMhw4:000000000000000000000000000000000000000000001ZK X-Hashcash: 1:20:140603:a.p.zijlstra@chello.nl::XxfVw6JgkP0KNnTS:0000000000000000000000000000000000000001FNH X-Hashcash: 1:20:140603:akpm@linux-foundation.org::wB5yNH11tdiIAyhK:0000000000000000000000000000000000001axv X-Hashcash: 1:20:140603:mingo@kernel.org::C6KOELj0dNuU/ick:02Y3b X-Hashcash: 1:20:140603:rostedt@goodmis.org::usNVJqg01S71FBwQ:0000000000000000000000000000000000000000002iPX X-Hashcash: 1:20:140603:rusty@rustcorp.com.au::5670RXWQ1gSePnkF:00000000000000000000000000000000000000002hV2 X-Hashcash: 1:20:140603:torvalds@linux-foundation.org::JvXQ1otFoIBC5adh:000000000000000000000000000000003Bgn X-Hashcash: 1:20:140603:hannes@cmpxchg.org::C5HOrTmWE3gVoOHe:00000000000000000000000000000000000000000003iiF X-Hashcash: 1:20:140603:mgorman@suse.de::kiz0ijd5aPu9OcPo:0085Tf X-Hashcash: 1:20:140603:hpa@zytor.com::42HCRbB7iN0jPIlL:00007rnd X-Hashcash: 1:20:140603:hughd@google.com::trhxoC0/SMzHi+rq:09ieY X-Hashcash: 1:20:140603:dave.hansen@intel.com::uKc/0U67QMNEQIxd:00000000000000000000000000000000000000008QBr X-Hashcash: 1:20:140603:riel@redhat.com::Z8qe6qBuuJm/ENfJ:00A7Oa X-Hashcash: 1:20:140603:linux-kernel@vger.kernel.org::fKnJ8RqBKtHPsLVg:000000000000000000000000000000000CF/a X-Hashcash: 1:20:140603:mst@redhat.com::Op7vP42VScd7XO7X:000L4bS Date: Tue, 03 Jun 2014 15:28:22 +0200 In-Reply-To: <20140530021247.GR10092@bbox> (Minchan Kim's message of "Fri, 30 May 2014 11:12:47 +0900") Message-ID: <87mwduqg09.fsf@rasmusvillemoes.dk> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Possibly stupid question: Is it true that any given task can only be using one wait_queue_t at a time? If so, would it be an idea to put a wait_queue_t into struct task_struct [maybe union'ed with a struct wait_bit_queue] and avoid allocating this 40 byte structure repeatedly on the stack. E.g., in one of Minchan's stack traces, there are two calls of mempool_alloc (which itself declares a wait_queue_t) and one try_to_free_pages (which is the only caller of throttle_direct_reclaim, which in turn uses wait_event_interruptible_timeout and wait_event_killable). Rasmus