Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757150AbaBFW6Y (ORCPT ); Thu, 6 Feb 2014 17:58:24 -0500 Received: from mail-pa0-f44.google.com ([209.85.220.44]:38782 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755098AbaBFW6X (ORCPT ); Thu, 6 Feb 2014 17:58:23 -0500 Date: Thu, 6 Feb 2014 14:58:21 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: Raghavendra K T , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , Jan Kara , Linus , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages In-Reply-To: <20140206145105.27dec37b16f24e4ac5fd90ce@linux-foundation.org> Message-ID: References: <1390388025-1418-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140206145105.27dec37b16f24e4ac5fd90ce@linux-foundation.org> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 6 Feb 2014, Andrew Morton wrote: > > --- a/mm/readahead.c > > +++ b/mm/readahead.c > > @@ -237,14 +237,32 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp, > > return ret; > > } > > > > +#define MAX_REMOTE_READAHEAD 4096UL > > /* > > * Given a desired number of PAGE_CACHE_SIZE readahead pages, return a > > * sensible upper limit. > > */ > > unsigned long max_sane_readahead(unsigned long nr) > > { > > - return min(nr, (node_page_state(numa_node_id(), NR_INACTIVE_FILE) > > - + node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2); > > + unsigned long local_free_page; > > + int nid; > > + > > + nid = numa_node_id(); If you're intending this to be cached for your calls into node_page_state() you need nid = ACCESS_ONCE(numa_node_id()). What's the downside of just using numa_mem_id() here instead which is usually "local memory to this memoryless node cpu" and forget about testing node_present_pages(nid)? > > + if (node_present_pages(nid)) { > > + /* > > + * We sanitize readahead size depending on free memory in > > + * the local node. > > + */ > > + local_free_page = node_page_state(nid, NR_INACTIVE_FILE) > > + + node_page_state(nid, NR_FREE_PAGES); > > + return min(nr, local_free_page / 2); > > + } > > + /* > > + * Readahead onto remote memory is better than no readahead when local > > + * numa node does not have memory. We limit the readahead to 4k > > + * pages though to avoid trashing page cache. > > + */ > > + return min(nr, MAX_REMOTE_READAHEAD); > > } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/