From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Williams Subject: Re: [PATCH 21/29] ioat2,3: dynamically resize descriptor ring Date: Tue, 15 Sep 2009 16:07:05 -0700 Message-ID: References: <20090904022733.32667.77626.stgit@dwillia2-linux.ch.intel.com> <20090904023216.32667.55942.stgit@dwillia2-linux.ch.intel.com> <129600E5E5FB004392DDC3FB599660D7B5548192@irsmsx504.ger.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: "linux-kernel@vger.kernel.org" , "linux-raid@vger.kernel.org" , "netdev@vger.kernel.org" To: "Sosnowski, Maciej" Return-path: In-Reply-To: <129600E5E5FB004392DDC3FB599660D7B5548192@irsmsx504.ger.corp.intel.com> Sender: linux-raid-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, Sep 14, 2009 at 8:00 AM, Sosnowski, Maciej wrote: > Making the max_alloc_order a module parameter gives impression > that it can be modified by an user, including making it larger than default. > The default is however its maximum value, which may be confusing. > Why not to use parameter only as the upper limit? It is the upper limit. The user can limit the upper size of the descriptor ring by setting this to a value less than 16. By default it is the maximum ring size that the driver/hardware* supports. Specifying values greater than 16 are not supported by the so we need enforce a ceiling at 16. -- Dan * We could support ring sizes larger than 1 << 16 but we would need to extra logic to ensure that the pending count never exceeded 1 << 16. Simpler I think to just limit the maximum ring size.