Message-ID: <18472b72-c64f-59b5-f767-d965f0264ef0@redhat.com>
Date:   Tue, 30 Nov 2021 15:51:37 +0100
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Subject: Re: [PATCH v1 0/2] virtio-mem: prepare for granularity smaller than
 MAX_ORDER - 1
Content-Language: en-US
To:     Zi Yan <ziy@nvidia.com>
Cc:     linux-kernel@vger.kernel.org,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Gavin Shan <gshan@redhat.com>, Hui Zhu <teawater@gmail.com>,
        Eric Ren <renzhengeek@gmail.com>,
        Sebastien Boeuf <sebastien.boeuf@intel.com>,
        Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
        Wei Yang <richard.weiyang@linux.alibaba.com>,
        virtualization@lists.linux-foundation.org, linux-mm@kvack.org
References: <20211126134209.17332-1-david@redhat.com>
 <F0D31D41-7843-4313-8264-E1C97979471B@nvidia.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <F0D31D41-7843-4313-8264-E1C97979471B@nvidia.com>
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On 29.11.21 17:47, Zi Yan wrote:
> On 26 Nov 2021, at 8:42, 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.
>>
>> Tested with ZONE_MOVABLE after removing the MAX_ORDER - 1 granularity
>> limitation in virtio-mem, and using different device block sizes (2MiB,
>> 4MiB, 8MiB).
>>
>> [1] https://lkml.kernel.org/r/20211115193725.737539-1-zi.yan@sent.com
> 
> The patchset looks good to me. Thanks. Reviewed-by: Zi Yan <ziy@nvidia.com>

Thanks a lot!

-- 
Thanks,

David / dhildenb