Message-ID: <4102154a-1e49-54d9-b18f-c41da84e643e@linux.alibaba.com>
Date:   Tue, 21 Mar 2023 19:37:45 +0800
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Subject: Re: [PATCH v2 0/6] tmpfs: add the option to disable swap
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     hughd@google.com, akpm@linux-foundation.org, willy@infradead.org,
        brauner@kernel.org, linux-mm@kvack.org, p.raghav@samsung.com,
        da.gomez@samsung.com, a.manzanares@samsung.com, dave@stgolabs.net,
        yosryahmed@google.com, keescook@chromium.org,
        patches@lists.linux.dev, linux-kernel@vger.kernel.org
References: <20230309230545.2930737-1-mcgrof@kernel.org>
 <e1de614b-25e1-5c21-933a-880412ac7421@linux.alibaba.com>
 <ZBdxWsrYfPgBG6NX@bombadil.infradead.org>
 <edb78eea-a9a2-5c62-d203-6f2be39757d2@linux.alibaba.com>
 <ZBjR15Tr1o98crup@bombadil.infradead.org>
From:   haoxin <xhao@linux.alibaba.com>
In-Reply-To: <ZBjR15Tr1o98crup@bombadil.infradead.org>
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在 2023/3/21 上午5:36, Luis Chamberlain 写道:
> On Mon, Mar 20, 2023 at 07:14:22PM +0800, haoxin wrote:
>> 在 2023/3/20 上午4:32, Luis Chamberlain 写道:
>>> On Tue, Mar 14, 2023 at 10:46:28AM +0800, haoxin wrote:
>>>> All these series looks good to me and i do some test on my virtual machine
>>>> it works well.
>>>>
>>>> so please add Tested-by: Xin Hao<xhao@linux.alibaba.com>  .
>>>>
>>>> just one question, if tmpfs pagecache occupies a large amount of memory, how
>>>> can we ensure successful memory reclamation in case of memory shortage?
>>> If you're disabling swap then you know the only thing you can do is
>>> unmount if you want to help the VM, otherwise the pressure is just
>>> greater for the VM.
>> Un, what i mean is can we add a priority so that this type of pagecache is
>> reclaimed last ?
> That seems to be a classifier request for something much less aggressive
> than mapping_set_unevictable(). My patches *prior* to using mapping_set_unevictable()
> are I think closer to what it seems you want, but as noted before by
> folks, that also puts unecessary stress on the VM because just fail
> reclaim on our writepage().
>
>> Instead of just setting the parameter noswap to make it unreclaimed, because
>> if such pagecache which occupy big part of memory which can not be
>> reclaimed, it will cause OOM.
> You can't simultaneously retain possession of a cake and eat it, too,
> once you eat it, its gone and noswap eats the cake because of the
> suggestion / decision to follow through with mapping_set_unevictable().
>
> It sounds like you want to make mapping_set_unevictable() optional and
> deal with the possible stress incurred writepage() failing?
Yes, Just a personal idea, in any way, the current patch is an excellent 
implementation,  thank you very much.
>   Not quite
> sure what else to recommend here.
>
>    Luis