linux-kernel - Re: [PATCH v6 0/3] Directed kmem charging

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Date:   Tue, 19 Jun 2018 12:11:49 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Jan Kara <jack@...e.com>, Greg Thelen <gthelen@...gle.com>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v6 0/3] Directed kmem charging

Hi Shakeel,

this looks generally reasonable to me.

However, patch 1 introduces API that isn't used until patch 2 and 3,
which makes reviewing harder since you have to jump back and forth
between emails. Please fold patch 1 and introduce API along with the
users.

On Mon, Jun 18, 2018 at 10:13:24PM -0700, Shakeel Butt wrote:
> This patchset introduces memcg variant memory allocation functions.  The
> caller can explicitly pass the memcg to charge for kmem allocations.
> Currently the kernel, for __GFP_ACCOUNT memory allocation requests,
> extract the memcg of the current task to charge for the kmem allocation.
> This patch series introduces kmem allocation functions where the caller
> can pass the pointer to the remote memcg.  The remote memcg will be
> charged for the allocation instead of the memcg of the caller.  However
> the caller must have a reference to the remote memcg.  This patch series
> also introduces scope API for targeted memcg charging. So, all the
> __GFP_ACCOUNT alloctions within the specified scope will be charged to
> the given target memcg.

Can you open with the rationale for the series, i.e. the problem
statement (fsnotify and bh memory footprint), *then* follow with the
proposed solution?

Thanks!