Messages in this thread | | | Subject | Re: [PATCH v1] powerpc/pseries: CMM: Drop page array | From | David Hildenbrand <> | Date | Mon, 30 Sep 2019 09:52:15 +0200 |
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On 27.09.19 23:06, Michael Ellerman wrote: > > > On 27 September 2019 9:19:49 pm AEST, David Hildenbrand <david@redhat.com> wrote: >> On 25.09.19 09:37, David Hildenbrand wrote: >>> On 10.09.19 18:39, David Hildenbrand wrote: >>>> We can simply store the pages in a list (page->lru), no need for a >>>> separate data structure (+ complicated handling). This is how most >>>> other balloon drivers store allocated pages without additional >> tracking >>>> data. >>>> >>>> For the notifiers, use page_to_pfn() to check if a page is in the >>>> applicable range. plpar_page_set_loaned()/plpar_page_set_active() >> were >>>> called with __pa(page_address()) for now, I assume we can simply >> switch >>>> to page_to_phys() here. The pfn_to_kaddr() handling is now mostly >> gone. >>>> >>>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> >>>> Cc: Paul Mackerras <paulus@samba.org> >>>> Cc: Michael Ellerman <mpe@ellerman.id.au> >>>> Cc: Arun KS <arunks@codeaurora.org> >>>> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> >>>> Cc: Thomas Gleixner <tglx@linutronix.de> >>>> Cc: Andrew Morton <akpm@linux-foundation.org> >>>> Cc: Vlastimil Babka <vbabka@suse.cz> >>>> Signed-off-by: David Hildenbrand <david@redhat.com> >>>> --- >>>> >>>> Only compile-tested. I hope the page_to_phys() thingy is correct and >> I >>>> didn't mess up something else / ignoring something important why the >> array >>>> is needed. >>>> >>>> I stumbled over this while looking at how the memory isolation >> notifier is >>>> used - and wondered why the additional array is necessary. Also, I >> think >>>> by switching to the generic balloon compaction mechanism, we could >> get >>>> rid of the memory hotplug notifier and the memory isolation notifier >> in >>>> this code, as the migration capability of the inflated pages is the >> real >>>> requirement: >>>> commit 14b8a76b9d53346f2871bf419da2aaf219940c50 >>>> Author: Robert Jennings <rcj@linux.vnet.ibm.com> >>>> Date: Thu Dec 17 14:44:52 2009 +0000 >>>> >>>> powerpc: Make the CMM memory hotplug aware >>>> >>>> The Collaborative Memory Manager (CMM) module allocates >> individual pages >>>> over time that are not migratable. On a long running system >> this can >>>> severely impact the ability to find enough pages to support a >> hotplug >>>> memory remove operation. >>>> [...] >>>> >>>> Thoughts? >>> >>> Ping, is still feature still used at all? >>> >>> If nobody can test, any advise on which HW I need and how to trigger >> it? >>> >> >> So ... if CMM is no longer alive I propose ripping it out completely. >> Does anybody know if this feature is still getting used? Getting rid of >> the memory isolation notifier sounds desirable - either by scrapping >> CMM >> or by properly wiring up balloon compaction. > > It's still used AFAIK, but the people who wrote the code have left IBM, and I'm on leave. > > I'll be back in a week or so and will try and track down how to test it then. >
Thanks - sure, take your time. I'll try to play with wiring up balloon compaction in the meantime.
Cheers!
> cheers >
--
Thanks,
David / dhildenb
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