Messages in this thread | | | Date | Tue, 10 Jan 2017 15:48:44 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: page_alloc: Skip over regions of invalid pfns where possible |
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On Tue, 10 Jan 2017 23:37:53 +0000 James Hartley <james.hartley@imgtec.com> wrote:
> > On 06/01/17 22:43, Andrew Morton wrote: > > On Fri, 25 Nov 2016 18:55:18 +0000 Paul Burton <paul.burton@imgtec.com> wrote: > > > >> When using a sparse memory model memmap_init_zone() when invoked with > >> the MEMMAP_EARLY context will skip over pages which aren't valid - ie. > >> which aren't in a populated region of the sparse memory map. However if > >> the memory map is extremely sparse then it can spend a long time > >> linearly checking each PFN in a large non-populated region of the memory > >> map & skipping it in turn. > >> > >> When CONFIG_HAVE_MEMBLOCK_NODE_MAP is enabled, we have sufficient > >> information to quickly discover the next valid PFN given an invalid one > >> by searching through the list of memory regions & skipping forwards to > >> the first PFN covered by the memory region to the right of the > >> non-populated region. Implement this in order to speed up > >> memmap_init_zone() for systems with extremely sparse memory maps. > > Could we have a changelog which includes some timing measurements? > > That permits others to understand the value of this patch. > > > I have tested this patch on a virtual model of a Samurai CPU with a > sparse memory map. The kernel boot time drops from 109 to 62 seconds.
Thanks. Nice. I updated the changelog.
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