Date:   Tue, 30 Nov 2021 18:56:38 -0500
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org, Jason Wang <jasowang@redhat.com>,
        Zi Yan <ziy@nvidia.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
Subject: Re: [PATCH v1 0/2] virtio-mem: prepare for granularity smaller than
 MAX_ORDER - 1
Message-ID: <20211130185612-mutt-send-email-mst@kernel.org>
References: <20211126134209.17332-1-david@redhat.com>
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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?

> 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
> 
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Gavin Shan <gshan@redhat.com>
> Cc: Hui Zhu <teawater@gmail.com>
> Cc: Eric Ren <renzhengeek@gmail.com>
> Cc: Sebastien Boeuf <sebastien.boeuf@intel.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: virtualization@lists.linux-foundation.org
> Cc: linux-mm@kvack.org
> 
> David Hildenbrand (2):
>   virtio-mem: prepare page onlining code for granularity smaller than
>     MAX_ORDER - 1
>   virtio-mem: prepare fake page onlining code for granularity smaller
>     than MAX_ORDER - 1
> 
>  drivers/virtio/virtio_mem.c | 110 ++++++++++++++++++++++++------------
>  1 file changed, 74 insertions(+), 36 deletions(-)
> 
> -- 
> 2.31.1