linux-kernel - Re: [PATCH v1 0/2] virtio-mem: prepare for granularity smaller than MAX_ORDER

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Message-ID: <7afa01ef-9048-4636-6059-efed7fadc452@redhat.com>
Date:   Wed, 1 Dec 2021 09:24:37 +0100
From:   David Hildenbrand <david@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Jason Wang <jasowang@...hat.com>,
        Zi Yan <ziy@...dia.com>, Gavin Shan <gshan@...hat.com>,
        Hui Zhu <teawater@...il.com>, Eric Ren <renzhengeek@...il.com>,
        Sebastien Boeuf <sebastien.boeuf@...el.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 0/2] virtio-mem: prepare for granularity smaller than
 MAX_ORDER - 1

On 01.12.21 00:56, Michael S. Tsirkin wrote:
> On Fri, Nov 26, 2021 at 02:42:07PM +0100, David Hildenbrand wrote:
>> The virtio-mem driver currently supports logical hot(un)plug in
>> MAX_ORDER - 1 granularity (4MiB on x86-64) or bigger. We want to support
>> pageblock granularity (2MiB on x86-64), to make hot(un)plug even more
>> flexible, and to improve hotunplug when using ZONE_NORMAL.
>>
>> With pageblock granularity, we then have a granularity comparable to
>> hugepage ballooning. Further, there are ideas to increase MAX_ORDER, so
>> we really want to decouple it from MAX_ORDER.
>>
>> While ZONE_MOVABLE should mostly work already, alloc_contig_range() still
>> needs work to be able to properly handle pageblock granularity on
>> ZONE_NORMAL. This support is in the works [1], so let's prepare
>> virtio-mem for supporting smaller granularity than MAX_ORDER - 1.
> 
> is there value to merging this seprately? or should this just
> be part of that patchset?
> 

The value would be to give it additional testing ahead of time. But we
could just carry it along. Whatever you prefer. (I'd suggest merging it
right away)

-- 
Thanks,

David / dhildenb