Messages in this thread | | | Subject | Re: [PATCH v4] drivers/base/memory.c: cache blocks in radix tree to accelerate lookup | From | Don Dutile <> | Date | Thu, 16 Jan 2020 12:17:01 -0500 |
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On 1/16/20 10:28 AM, David Hildenbrand wrote: > On 16.01.20 16:22, Michal Hocko wrote: >> On Wed 15-01-20 20:09:48, David Hildenbrand wrote: >>> On 09.01.20 22:25, Scott Cheloha wrote: >>>> Searching for a particular memory block by id is an O(n) operation >>>> because each memory block's underlying device is kept in an unsorted >>>> linked list on the subsystem bus. >>>> >>>> We can cut the lookup cost to O(log n) if we cache the memory blocks in >>>> a radix tree. With a radix tree cache in place both memory subsystem >>>> initialization and memory hotplug run palpably faster on systems with a >>>> large number of memory blocks. >>>> >>>> Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com> >>>> Acked-by: David Hildenbrand <david@redhat.com> >>>> Acked-by: Nathan Lynch <nathanl@linux.ibm.com> >>>> Acked-by: Michal Hocko <mhocko@suse.com> >>> >>> Soooo, >>> >>> I just learned that radix trees are nowadays only a wrapper for xarray >>> (for quite a while already!), and that the xarray interface shall be >>> used in new code. >> >> Good point. I somehow didn't realize this would add more work for a >> later code refactoring. The mapping should be pretty straightforward. > > Yes it is. @Scott, care to send a fixup that does the mapping? > >> >> Thanks for noticing! > > Don noticed it, so thanks to him :) > Backporting XArray to RHEL-8, and continuing to support radix-tree api in RHEL-8 due to RHEL rulz, it wasn't stable/bug-free everyewhere, etc., was a challenge, thus my 'sensitivity' to seeing new radix-tree code upstream.
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