Messages in this thread | | | Date | Sat, 28 Sep 2019 07:06:37 +1000 | Subject | Re: [PATCH v1] powerpc/pseries: CMM: Drop page array | From | Michael Ellerman <> |
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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.
cheers -- Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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