From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>,
David Hildenbrand <david@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Michal Hocko <mhocko@kernel.org>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Peter Zijlstra <peterz@infradead.org>,
Steven Sistare <steven.sistare@oracle.com>
Subject: Re: [PATCH] x86/mm: use max memory block size with unaligned memory end
Date: Thu, 4 Jun 2020 18:27:52 -0400 [thread overview]
Message-ID: <20200604222752.ubwykq4himsjdult@ca-dmjordan1.us.oracle.com> (raw)
In-Reply-To: <72066bef-866a-c2a4-d536-4212c3344045@intel.com>
On Thu, Jun 04, 2020 at 01:00:55PM -0700, Dave Hansen wrote:
> On 6/4/20 11:12 AM, Daniel Jordan wrote:
> >> E.g., on powerpc that's 16MB so they have *a lot* of memory blocks.
> >> That's why that's not papering over the problem. Increasing the memory
> >> block size isn't always the answer.
> > Ok. If you don't mind, what's the purpose of hotplugging at that granularity?
> > I'm simply curious.
>
> FWIW, the 128MB on x86 came from the original sparsemem/hotplug
> implementation. It was the size of the smallest DIMM that my server
> system at the time would take. ppc64's huge page size was and is 16MB
> and that's also the granularity with which hypervisors did hot-add way
> back then. I'm not actually sure what they do now.
Interesting, that tells me a lot more than the "matt - 128 is convenient right
now" comment that has always weirdly stuck out at me.
> I actually can't think of anything that's *keeping* it at 128MB on x86
> though. We don't, for instance, require a whole section to be
> pfn_valid().
Hm, something to look into.
next prev parent reply other threads:[~2020-06-04 22:27 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-04 3:54 [PATCH] x86/mm: use max memory block size with unaligned memory end Daniel Jordan
2020-06-04 7:22 ` David Hildenbrand
2020-06-04 17:22 ` Daniel Jordan
2020-06-04 17:45 ` David Hildenbrand
2020-06-04 18:12 ` Daniel Jordan
2020-06-04 18:55 ` David Hildenbrand
2020-06-04 22:24 ` Daniel Jordan
2020-06-04 20:00 ` Dave Hansen
2020-06-04 22:27 ` Daniel Jordan [this message]
2020-06-05 7:44 ` David Hildenbrand
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