linux-kernel - RE: [PATCH 00/35] Enhance memory utilization with DMEMFS

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Date:   Mon, 12 Oct 2020 11:57:20 +0000
From:   "Zengtao (B)" <prime.zeng@...ilicon.com>
To:     "yulei.kernel@...il.com" <yulei.kernel@...il.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "naoya.horiguchi@....com" <naoya.horiguchi@....com>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>
CC:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xiaoguangrong.eric@...il.com" <xiaoguangrong.eric@...il.com>,
        "kernellwp@...il.com" <kernellwp@...il.com>,
        "lihaiwei.kernel@...il.com" <lihaiwei.kernel@...il.com>,
        Yulei Zhang <yuleixzhang@...cent.com>
Subject: RE: [PATCH 00/35] Enhance memory utilization with DMEMFS


> -----Original Message-----
> From: yulei.kernel@...il.com [mailto:yulei.kernel@...il.com]
> Sent: Thursday, October 08, 2020 3:54 PM
> To: akpm@...ux-foundation.org; naoya.horiguchi@....com;
> viro@...iv.linux.org.uk; pbonzini@...hat.com
> Cc: linux-fsdevel@...r.kernel.org; kvm@...r.kernel.org;
> linux-kernel@...r.kernel.org; xiaoguangrong.eric@...il.com;
> kernellwp@...il.com; lihaiwei.kernel@...il.com; Yulei Zhang
> Subject: [PATCH 00/35] Enhance memory utilization with DMEMFS
> 
> From: Yulei Zhang <yuleixzhang@...cent.com>
> 
> In current system each physical memory page is assocaited with
> a page structure which is used to track the usage of this page.
> But due to the memory usage rapidly growing in cloud environment,
> we find the resource consuming for page structure storage becomes
> highly remarkable. So is it an expense that we could spare?
> 
> This patchset introduces an idea about how to save the extra
> memory through a new virtual filesystem -- dmemfs.
> 
> Dmemfs (Direct Memory filesystem) is device memory or reserved
> memory based filesystem. This kind of memory is special as it
> is not managed by kernel and most important it is without 'struct page'.
> Therefore we can leverage the extra memory from the host system
> to support more tenants in our cloud service.
> 
> We uses a kernel boot parameter 'dmem=' to reserve the system
> memory when the host system boots up, the details can be checked
> in /Documentation/admin-guide/kernel-parameters.txt.
> 
> Theoretically for each 4k physical page it can save 64 bytes if
> we drop the 'struct page', so for guest memory with 320G it can
> save about 5G physical memory totally.

Sounds interesting, but seems your patch only support x86, have you
 considered aarch64?

Regards
Zengtao