From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by kanga.kvack.org (Postfix) with ESMTP id 039646B0037 for ; Thu, 6 Feb 2014 17:58:24 -0500 (EST) Received: by mail-pa0-f51.google.com with SMTP id ld10so2340874pab.10 for ; Thu, 06 Feb 2014 14:58:24 -0800 (PST) Received: from mail-pa0-x22b.google.com (mail-pa0-x22b.google.com [2607:f8b0:400e:c03::22b]) by mx.google.com with ESMTPS id sd3si2583531pbb.342.2014.02.06.14.58.22 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 06 Feb 2014 14:58:23 -0800 (PST) Received: by mail-pa0-f43.google.com with SMTP id rd3so2324137pab.16 for ; Thu, 06 Feb 2014 14:58:22 -0800 (PST) Date: Thu, 6 Feb 2014 14:58:21 -0800 (PST) From: David Rientjes 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: 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 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org