From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leon Romanovsky Subject: Re: [PATCH 00/16] IB/hfi1: Add a page pinning cache for PSM sdma Date: Thu, 10 Mar 2016 06:56:09 +0200 Message-ID: <20160310045609.GC1977@leon.nu> References: <20160308191210.30542.91885.stgit@scvm10.sc.intel.com> <20160309002157.GA20105@phlsvsds.ph.intel.com> <20160309050731.GM13396@leon.nu> <20160309192109.GB15031@phlsvsds.ph.intel.com> Reply-To: leon-2ukJVAZIZ/Y@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20160309192109.GB15031-W4f6Xiosr+yv7QzWx2u06xL4W9x8LtSr@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Dennis Dalessandro Cc: Or Gerlitz , Doug Ledford , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On Wed, Mar 09, 2016 at 02:21:10PM -0500, Dennis Dalessandro wrote: > On Wed, Mar 09, 2016 at 07:07:31AM +0200, Leon Romanovsky wrote: > >On Tue, Mar 08, 2016 at 07:21:58PM -0500, Dennis Dalessandro wrote: > >>On Tue, Mar 08, 2016 at 10:56:48PM +0200, Or Gerlitz wrote: > >>>On Tue, Mar 8, 2016 at 9:14 PM, Dennis Dalessandro > >>> wrote: > >>> > >>>>This patch series adds a performance improvement to user SDMA transfers from > >>>>PSM applications by caching user buffer pages after pinning them. Subsequent > >>>>uses of the same user buffer will not incur the cost of pinning the same pages > >>>>again. Additionally, the cost of unpinning the same pages is avoided. Buffer > >>>>pages are unpinned when the context is torn down or when the driver determines > >>>>that the buffer should be evicted from the cache. Cache evictions happen when > >>>>there is a request for a new, uncached buffer and the current size of the cache > >>>>has reached a pre-defined limit. > >>> > >>>If indeed there's a need for such a pin down cache, it should have > >>>been implemented in the IB core, b/c both the problem and the solution > >>>are generic and have nothing to do with certain device driver. > >> > >>Since this is for psm it has nothing to do with the IB core. I fail to see > >>what that would achieve. > > > >I tend to agree with Or, your proposal goes far beyond the driver code. > >Do you expect that all drivers which will be needed to support PSM will > >implement (copy/paste) the same generic logic? > > We should not be putting something which is specific to PSM in the IB core. > We feel the driver is the most appropriate place for this. To use cache logic - yes To implement cache logic - no Can you share with us the technical justification of implementing general memory management cache mechanism in driver and not in appropriate layer (IB/core and/or MM)? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html