From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rahul Lakkireddy Subject: Re: [RFC PATCH 2/3] x86/io: implement 256-bit IO read and write Date: Wed, 21 Mar 2018 17:58:08 +0530 Message-ID: <20180321122807.GB3245@chelsio.com> References: <6ec3e7e0c70e85a804933f27bb4275d5363c044b.1521469118.git.rahul.lakkireddy@chelsio.com> <20180320133206.GB25574@chelsio.com> <5f43882155104f50bbd2e5cf63d432f2@AcuMS.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Thomas Gleixner , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "mingo@redhat.com" , "hpa@zytor.com" , "davem@davemloft.net" , "akpm@linux-foundation.org" , "torvalds@linux-foundation.org" , Ganesh GR , Nirranjan Kirubaharan , Indranil Choudhury To: David Laight Return-path: Content-Disposition: inline In-Reply-To: <5f43882155104f50bbd2e5cf63d432f2@AcuMS.aculab.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tuesday, March 03/20/18, 2018 at 20:10:19 +0530, David Laight wrote: > From: Rahul Lakkireddy > > Sent: 20 March 2018 13:32 > ... > > On High Availability Server, the logs of the failing system must be > > collected as quickly as possible. So, we're concerned with the amount > > of time taken to collect our large on-chip memory. We see improvement > > in doing 256-bit reads at a time. > > Two other options: > > 1) Get the device to DMA into host memory. > Unfortunately, our device doesn't support doing DMA of on-chip memory. > 2) Use mmap() (and vm_iomap_memory() in your driver) to get direct > userspace access to the (I assume) PCIe memory space. > You can then use whatever copy instructions the cpu has. > (Just don't use memcpy().) > We also need to collect this in kernel space i.e. from crash recovery kernel. Thanks, Rahul