linux-kernel - Re: [PATCH RFC] virtio_balloon: conservative balloon page shrinking

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Date:   Thu, 6 Feb 2020 10:49:22 +0100
From:   David Hildenbrand <david@...hat.com>
To:     "Wang, Wei W" <wei.w.wang@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Cc:     "tysand@...gle.com" <tysand@...gle.com>,
        "mst@...hat.com" <mst@...hat.com>,
        "alexander.h.duyck@...ux.intel.com" 
        <alexander.h.duyck@...ux.intel.com>,
        "rientjes@...gle.com" <rientjes@...gle.com>,
        "mhocko@...nel.org" <mhocko@...nel.org>,
        "namit@...are.com" <namit@...are.com>,
        "penguin-kernel@...ove.SAKURA.ne.jp" 
        <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: Re: [PATCH RFC] virtio_balloon: conservative balloon page shrinking

On 06.02.20 10:44, Wang, Wei W wrote:
> On Thursday, February 6, 2020 5:32 PM, David Hildenbrand wrote:
>>
>> If the page cache is empty, a drop_slab() will deflate the whole balloon if I
>> am not wrong.
>>
>> Especially, a echo 3 > /proc/sys/vm/drop_caches
>>
>> will first drop the page cache and then drop_slab()
> 
> Then that's the problem of "echo 3 > /proc/sys/vm/drop_cache" itself. It invokes other shrinkers as well (if considered an issue), need to be tweaked in the mm.

In short, I don't like this approach as long as a drop_slab() can
deflate the whole balloon and don't think this is the right approach then.


-- 
Thanks,

David / dhildenb