From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 03463B7168 for ; Thu, 18 Nov 2010 04:15:19 +1100 (EST) Subject: Re: [PATCH] powerpc: Per process DSCR Mime-Version: 1.0 (Apple Message framework v1081) Content-Type: text/plain; charset=us-ascii From: Kumar Gala In-Reply-To: <20101117113130.3702897c@kryten> Date: Wed, 17 Nov 2010 11:15:07 -0600 Message-Id: <9BF17613-A893-4FE8-97BB-3BDCDF740591@kernel.crashing.org> References: <20101117113130.3702897c@kryten> To: Anton Blanchard Cc: paulus@samba.org, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Nov 16, 2010, at 6:31 PM, Anton Blanchard wrote: > In order to add per process control of the DSCR, the following patch = emulates > read/write of the DSCR from userspace and saves and restores it on = context > switch. We add emulated stats to track how many times we do this. >=20 > While writing this patch a few things were apparent: >=20 > - How will this work with the global DSCR setting in > /sys/devices/system/cpu/cpu*/dscr? Do we deprecate it? One thought is > to add a new sysfs entry (eg dscr_enabled), which tells us to > override any per process settings. Another way would be to overload > the dscr sysfs entry and make -1 mean the system wide dscr setting is > disabled. >=20 > - Do we need an out of band method of changing the DSCR so another > process or could modify it? We may want to modify the DSCR of a long > running process, eg a HPC job. >=20 > - To improve context switch speed we should probably check the old and > new DSCR values are identical and avoid the SPR write. >=20 > Signed-off-by: Anton Blanchard We don't have no stinking DSCR ;). Would like this to be #ifdef = CONFIG_PPC_BOOK3S_64. - k=