From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 023726B005A for ; Tue, 26 May 2009 17:31:04 -0400 (EDT) Date: Tue, 26 May 2009 14:30:58 -0700 From: Andrew Morton Subject: Re: [PATCH] lib : provide a more precise radix_tree_gang_lookup_slot Message-Id: <20090526143058.c59e6dc1.akpm@linux-foundation.org> In-Reply-To: <1243223635-3449-1-git-send-email-shijie8@gmail.com> References: <1243223635-3449-1-git-send-email-shijie8@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Huang Shijie Cc: cl@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Mon, 25 May 2009 11:53:55 +0800 Huang Shijie wrote: > The origin radix_tree_gang_lookup_slot() tries to > lookup max_items slots.But there are maybe holes for > find_get_pages_contig() which will only use the contiguous part. > > So a more precise radix_tree_gang_lookup_slot() is needed > to avoid unneccessary search work. > OK.. > diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h > index 355f6e8..03e25f4 100644 > --- a/include/linux/radix-tree.h > +++ b/include/linux/radix-tree.h > @@ -164,7 +164,8 @@ radix_tree_gang_lookup(struct radix_tree_root *root, void **results, > unsigned long first_index, unsigned int max_items); > unsigned int > radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results, > - unsigned long first_index, unsigned int max_items); > + unsigned long first_index, unsigned int max_items, > + int contig); Variable `contig' could have the type `bool'. Did you consider and reject that option, or just didn't think of it? > ... > + if (contig) > + goto out; > + > + } else if (contig) { > + index--; > + goto out; > + > + if (contig) { > + if (slots_found == 0) > + break; > + if (next_index & RADIX_TREE_MAP_MASK) > + break; > + } > - (void ***)pages, start, nr_pages); > + (void ***)pages, start, nr_pages, 0); > - (void ***)pages, index, nr_pages); > + (void ***)pages, index, nr_pages, 1); The patch adds cycles in some cases and saves them in others. Does the saving exceed the adding? How do we know that the patch is a net benefit? -- 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