On Mon 10-09-18 20:02:05, Shuah Khan wrote: > 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.
OK, that is more clear. I still believe that you either have to have a very good control over memory allocations or a good luck to not see unexpected kernel allocations in your reserved memory which might easily break guarantees you would like to accomplish. -- Michal Hocko SUSE Labs
