From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx109.postini.com [74.125.245.109]) by kanga.kvack.org (Postfix) with SMTP id 7464D6B0008 for ; Tue, 22 Jan 2013 20:50:02 -0500 (EST) Date: Wed, 23 Jan 2013 10:49:59 +0900 From: Minchan Kim Subject: Re: [PATCH] Subtract min_free_kbytes from dirtyable memory Message-ID: <20130123014959.GB2723@blaptop> References: <201301210315.r0L3FnGV021298@como.maths.usyd.edu.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201301210315.r0L3FnGV021298@como.maths.usyd.edu.au> Sender: owner-linux-mm@kvack.org List-ID: To: paul.szabo@sydney.edu.au Cc: linux-mm@kvack.org, 695182@bugs.debian.org, linux-kernel@vger.kernel.org On Mon, Jan 21, 2013 at 02:15:49PM +1100, paul.szabo@sydney.edu.au wrote: > When calculating amount of dirtyable memory, min_free_kbytes should be > subtracted because it is not intended for dirty pages. So what's the effect for user? It would be better to include that in description if possible. > > Using an "extern int" because that is the only interface to some such > sysctl values. > > (This patch does not solve the PAE OOM issue.) > > Paul Szabo psz@maths.usyd.edu.au http://www.maths.usyd.edu.au/u/psz/ > School of Mathematics and Statistics University of Sydney Australia > > Reported-by: Paul Szabo > Reference: http://bugs.debian.org/695182 > Signed-off-by: Paul Szabo > > --- mm/page-writeback.c.old 2012-12-06 22:20:40.000000000 +1100 > +++ mm/page-writeback.c 2013-01-21 13:57:05.000000000 +1100 > @@ -343,12 +343,16 @@ > unsigned long determine_dirtyable_memory(void) > { > unsigned long x; > + extern int min_free_kbytes; > > x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); > > if (!vm_highmem_is_dirtyable) > x -= highmem_dirtyable_memory(x); > > + /* Subtract min_free_kbytes */ > + x -= min(x, min_free_kbytes >> (PAGE_SHIFT - 10)); It seems you saw old kernel. Current kernel includes following logic. static unsigned long global_dirtyable_memory(void) { unsigned long x; x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); x -= min(x, dirty_balance_reserve); if (!vm_highmem_is_dirtyable) x -= highmem_dirtyable_memory(x); return x + 1; /* Ensure that we never return 0 */ } And dirty_lanace_reserve already includes high_wmark_pages. Look at calculate_totalreserve_pages. So I think we don't need this patch. Thanks. > + > return x + 1; /* Ensure that we never return 0 */ > } > > -- > 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 -- Kind regards, Minchan Kim -- 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