linux-kernel - Re: Is it possible to implement the per-node page cache for programs/libraries?

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Message-ID: <CAGsJ_4ySjL9SWaquP4BoWROZ=qPFgyTKnPWuSP_LD08RZB7uzg@mail.gmail.com>
Date:   Thu, 2 Sep 2021 12:15:06 +1200
From:   Barry Song <21cnbao@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Huang Shijie <shijie@...amperecomputing.com>,
        Shijie Huang <shijie@...eremail.onmicrosoft.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Barry Song <song.bao.hua@...ilicon.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Frank Wang <zwang@...erecomputing.com>
Subject: Re: Is it possible to implement the per-node page cache for programs/libraries?

On Thu, Sep 2, 2021 at 12:00 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> 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.

Not quite sure I catch your point. In case we are running mysql on a
machine with 128 cores
(4numa, 32cores in each numa), how will the reflink help the only
mysql process to leverage
its local libc copy?

Thanks
Barry