From mboxrd@z Thu Jan 1 00:00:00 1970 From: shuah@kernel.org (Shuah Khan) Date: Mon, 10 Sep 2018 20:02:05 -0600 Subject: [PATCH] arm64: add NUMA emulation support In-Reply-To: <20180910134845.GH10951@dhcp22.suse.cz> References: <20180824230559.32336-1-shuah@kernel.org> <20180828174011.GE20375@arm.com> <20180829110802.GD10349@dhcp22.suse.cz> <20180905064252.GW14951@dhcp22.suse.cz> <20180907083452.GC19621@dhcp22.suse.cz> <20180910134845.GH10951@dhcp22.suse.cz> Message-ID: <4d7beb50-f778-507a-4c3c-f6de92f8cfb9@kernel.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Michal, On 09/10/2018 07:48 AM, Michal Hocko wrote: > On Fri 07-09-18 16:30:59, Shuah Khan wrote: >> On 09/07/2018 02:34 AM, Michal Hocko wrote: >>> On Thu 06-09-18 15:53:34, Shuah Khan wrote: [....] >> >> In addition to isolation, being able to reserve a block instead is one of the >> issues I am looking to address. Unfortunately memory cgroups won't address that >> issue. > > Could you be more specific why you need reservations other than > isolation. > Taking automotive as a specific example, there are two classes of applications: 1. critical applications that must run 2. Infotainment and misc. user-space. In this case, being able to reserve a block of memory for critical applications will ensure the memory is available for them. If a critical application has to restart and/or when an on-demand critical application starts, it might not be able to allocate memory if it is not reserved. When a flat system has multiple memory blocks, with NUMA emulation in conjunction with cpusets, one or more block can be reserved for critical applications configuring a set of cpus and one of more memory nodes for them. Memory cgroups will not support such reservation. Hope this helps explain the use-case I am trying to address with this patch. thanks, -- Shuah