From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754584Ab1A2Irr (ORCPT ); Sat, 29 Jan 2011 03:47:47 -0500 Received: from courier.cs.helsinki.fi ([128.214.9.1]:52406 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752876Ab1A2Irq (ORCPT ); Sat, 29 Jan 2011 03:47:46 -0500 Subject: Re: [PATCH 1/7] [v2] zram/vmalloc: Correct tunings to enable use with 64K pages From: Pekka Enberg To: Robert Jennings Cc: Nitin Gupta , Greg Kroah-Hartman , devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org In-Reply-To: <20110128145726.GB2062@linux.vnet.ibm.com> References: <20110128145602.GA2062@linux.vnet.ibm.com> <20110128145726.GB2062@linux.vnet.ibm.com> Content-Type: text/plain; charset="ISO-8859-1" Date: Sat, 29 Jan 2011 10:47:44 +0200 Message-ID: <1296290864.30654.5.camel@jaguar> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-01-28 at 08:57 -0600, Robert Jennings wrote: > xvmalloc will not currently function with 64K pages. Newly allocated > pages will be inserted at an offset beyond the end of the first-level > index. This tuning is needed to properly size the allocator for 64K > pages. > > The default 3 byte shift results in a second level list size which can not > be indexed using the 64 bits of the flbitmap in the xv_pool structure. > The shift must increase to 4 bytes between second level list entries to > fit the size of the first level bitmap. > > Here are a few statistics for structure sizes on 32- and 64-bit CPUs > with 4KB and 64KB page sizes. > > bits_per_long 32 64 64 > page_size 4,096 4,096 65,535 > xv_align 4 8 8 > fl_delta 3 3 4 > num_free_lists 508 508 4,094 > xv_pool size 4,144b 8,216b 66,040b > per object overhead 32 64 64 > zram struct 0.5GB disk 512KB 1024KB 64KB > > This patch maintains the current tunings for 4K pages, adds an optimal > sizing for 64K pages and adds a safe tuning for any other page sizes. > > Signed-off-by: Robert Jennings Reviewed-by: Pekka Enberg