linux-kernel - Re: [PATCH 1/1] net/ipv4/inet_fragment: Batch fqdir destroy works

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Date:   Thu, 10 Dec 2020 07:43:29 +0100
From:   SeongJae Park <sjpark@...zon.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     SeongJae Park <sjpark@...zon.com>, <davem@...emloft.net>,
        SeongJae Park <sjpark@...zon.de>, <kuznet@....inr.ac.ru>,
        <paulmck@...nel.org>, <netdev@...r.kernel.org>,
        <rcu@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] net/ipv4/inet_fragment: Batch fqdir destroy works

On Wed, 9 Dec 2020 15:16:59 -0800 Jakub Kicinski <kuba@...nel.org> wrote:

> On Tue, 8 Dec 2020 10:45:29 +0100 SeongJae Park wrote:
> > From: SeongJae Park <sjpark@...zon.de>
> > 
> > In 'fqdir_exit()', a work for destruction of the 'fqdir' is enqueued.
> > The work function, 'fqdir_work_fn()', calls 'rcu_barrier()'.  In case of
> > intensive 'fqdir_exit()' (e.g., frequent 'unshare(CLONE_NEWNET)'
> > systemcalls), this increased contention could result in unacceptably
> > high latency of 'rcu_barrier()'.  This commit avoids such contention by
> > doing the destruction in batched manner, as similar to that of
> > 'cleanup_net()'.
> > 
> > Signed-off-by: SeongJae Park <sjpark@...zon.de>
> 
> Looks fine to me, but you haven't CCed Florian or Eric who where the
> last two people to touch this function. Please repost CCing them and
> fixing the nit below, thanks!

Thank you for let me know that.  I will send the next version so.

> 
> >  static void fqdir_work_fn(struct work_struct *work)
> >  {
> > -	struct fqdir *fqdir = container_of(work, struct fqdir, destroy_work);
> > -	struct inet_frags *f = fqdir->f;
> > +	struct llist_node *kill_list;
> > +	struct fqdir *fqdir;
> > +	struct inet_frags *f;
> 
> nit: reorder fqdir and f to keep reverse xmas tree variable ordering.

Hehe, ok, I will. :)


Thanks,
SeongJae Park