On Thu, 17 Aug 2017 14:59:20 -0700 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > On Thu, Aug 17, 2017 at 2:55 PM, Jerome Glisse <jglisse@xxxxxxxxxx> wrote: > > On Thu, Aug 17, 2017 at 02:39:16PM -0700, Andrew Morton wrote: > >> On Wed, 16 Aug 2017 20:05:29 -0400 J__r__me Glisse <jglisse@xxxxxxxxxx> wrote: > >> > >> > Heterogeneous Memory Management (HMM) (description and justification) > >> > >> The patchset adds 55 kbytes to x86_64's mm/*.o and there doesn't appear > >> to be any way of avoiding this overhead, or of avoiding whatever > >> runtime overheads are added. > > > > HMM have already been integrated in couple of Red Hat kernel and AFAIK there > > is no runtime performance issue reported. Thought the RHEL version does not > > use static key as Dan asked. > > > >> > >> It also adds 18k to arm's mm/*.o and arm doesn't support HMM at all. > >> > >> So that's all quite a lot of bloat for systems which get no benefit from > >> the patchset. What can we do to improve this situation (a lot)? > > > > I will look into why object file grow so much on arm. My guess is that the > > new migrate code is the bulk of that. I can hide the new page migration code > > behind a kernel configuration flag. > > Shouldn't we completely disable all of it unless there is a driver in > the kernel that selects it? That would be typical (and nice). I'm not sure that Red Hat's decision is a broad enough guide here. Someone who is using Linux to make a cash register or a thermostat faces different tradeoffs... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
