From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ea0-f174.google.com (mail-ea0-f174.google.com [209.85.215.174]) by kanga.kvack.org (Postfix) with ESMTP id 5F49F6B0035 for ; Fri, 10 Jan 2014 03:36:59 -0500 (EST) Received: by mail-ea0-f174.google.com with SMTP id b10so1902040eae.19 for ; Fri, 10 Jan 2014 00:36:58 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id n47si8553283eef.199.2014.01.10.00.36.58 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 10 Jan 2014 00:36:58 -0800 (PST) Date: Fri, 10 Jan 2014 09:36:56 +0100 From: Jan Kara Subject: Re: [RFC PATCH V4] mm readahead: Fix readahead fail for no local memory and limit readahead pages Message-ID: <20140110083656.GC26378@quack.suse.cz> References: <1389295490-28707-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1389295490-28707-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Raghavendra K T Cc: Andrew Morton , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , jack@suse.cz, Linus , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri 10-01-14 00:54:50, Raghavendra K T wrote: > 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% OK, looks good to me. You can add: Reviewed-by: Jan Kara Honza > > 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 > -- Jan Kara SUSE Labs, CR -- 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