linux-kernel - Re: [PATCH] mm/memcg: Properly handle memcg_stock access for PREEMPT

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Date:   Thu, 9 Dec 2021 21:47:16 -0500
From:   Waiman Long <longman@...hat.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] mm/memcg: Properly handle memcg_stock access for
 PREEMPT_RT

On 12/9/21 21:06, Waiman Long wrote:
> Direct calls to local_irq_{save/restore}() and preempt_{enable/disable}()
> are not appropriate for PREEMPT_RT. To provide better PREEMPT_RT support,
> change local_irq_{save/restore}() to local_lock_irq{save/restore}() and
> add a local_lock_t to struct memcg_stock_pcp.
>
> Also disable the task and interrupt context optimization for obj_stock as
> there will be no performance gain in the case of PREEMPT_RT. In this case,
> task obj_stock will be there but remain unused.
>
> Signed-off-by: Waiman Long <longman@...hat.com>
> ---
>   mm/memcontrol.c | 41 ++++++++++++++++++++++-------------------
>   1 file changed, 22 insertions(+), 19 deletions(-)

Sorry, this doesn't apply to linux-next as it conflicts with a previous 
patch that I sent out. Will send out a v2 soon.

-Longman