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Date:   Thu, 2 Sep 2021 00:58:02 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Huang Shijie <shijie@os.amperecomputing.com>
Cc:     Shijie Huang <shijie@amperemail.onmicrosoft.com>,
        torvalds@linux-foundation.org, viro@zeniv.linux.org.uk,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        song.bao.hua@hisilicon.com, linux-kernel@vger.kernel.org,
        Frank Wang <zwang@amperecomputing.com>
Subject: Re: Is it possible to implement the per-node page cache for
 programs/libraries?
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On Wed, Sep 01, 2021 at 02:25:34PM +0000, Huang Shijie wrote:
> On Wed, Sep 01, 2021 at 01:30:45PM +0000, Huang Shijie wrote:
> > On Wed, Sep 01, 2021 at 04:25:01AM +0100, Matthew Wilcox wrote:
> > > On Wed, Sep 01, 2021 at 11:07:41AM +0800, Shijie Huang wrote:
> > > >     In the NUMA, we only have one page cache for each file. For the
> > > > program/shared libraries, the
> > > > remote-access delays longer then the  local-access.
> > > > 
> > > > So, is it possible to implement the per-node page cache for
> > > > programs/libraries?
> > > 
> > > At this point, we have no way to support text replication within a
> > > process.  So what you're suggesting (if implemented) would work for
> > 
> > I created a glibc patch which can do the text replication within a process.
> The "text replication" means the shared libraries, not program itself.

Thinking about it some more, if you're ok with it only being shared
libraries, you can do this:

for i in `seq 0 3`; do \
	cp --reflink=always /lib/x86_64-linux-gnu/libc.so.6 \
		/lib/x86_64-linux-gnu/libc.so.6.numa$i; \
done

Reflinked files don't share page cache, so you can do this all in
userspace with no kernel changes.