Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756989AbaAITRy (ORCPT ); Thu, 9 Jan 2014 14:17:54 -0500 Received: from e38.co.us.ibm.com ([32.97.110.159]:59367 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755295AbaAITRl (ORCPT ); Thu, 9 Jan 2014 14:17:41 -0500 From: Raghavendra K T To: Andrew Morton , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , jack@suse.cz, Linus Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Raghavendra K T Subject: [RFC PATCH V4] mm readahead: Fix readahead fail for no local memory and limit readahead pages Date: Fri, 10 Jan 2014 00:54:50 +0530 Message-Id: <1389295490-28707-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.11.7 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14010919-1344-0000-0000-000004CB8C14 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We limit the number of readahead pages to 4k. max_sane_readahead returns zero on the cpu having no local memory node. Fix that by returning a sanitized number of pages viz., minimum of (requested pages, 4k, number of local free pages) Result: fadvise experiment with FADV_WILLNEED on a x240 machine with 1GB testfile 32GB* 4G RAM numa machine ( 12 iterations) yielded kernel Avg Stddev base 7.264 0.56% patched 7.285 1.14% Signed-off-by: Raghavendra K T --- mm/readahead.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) V4: incorporated 16MB limit suggested by Linus for readahead and fixed transitioning to large readahead anomaly pointed by Andrew Morton with Honza's suggestion. Test results shows no significant overhead with the current changes. (Do I have to break patches into two??) Suggestions/Comments please let me know. diff --git a/mm/readahead.c b/mm/readahead.c index 7cdbb44..2f561a0 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -237,14 +237,30 @@ 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; + unsigned long sane_nr; + int nid; + + nid = numa_node_id(); + sane_nr = min(nr, MAX_REMOTE_READAHEAD); + + local_free_page = node_page_state(nid, NR_INACTIVE_FILE) + + node_page_state(nid, NR_FREE_PAGES); + + /* + * Readahead onto remote memory is better than no readahead when local + * numa node does not have memory. We sanitize readahead size depending + * on free memory in the local node but limiting to 4k pages. + */ + return node_present_pages(nid) ? + min(sane_nr, local_free_page / 2) : sane_nr; } /* -- 1.7.11.7 -- 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/