From: Michal Hocko <mhocko@kernel.org>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
rcu@vger.kernel.org, willy@infradead.org, peterz@infradead.org,
neilb@suse.com, vbabka@suse.cz, mgorman@suse.de,
Andrew Morton <akpm@linux-foundation.org>,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH RFC] rcu/tree: Use GFP_MEMALLOC for alloc memory to free memory pattern
Date: Tue, 31 Mar 2020 17:34:50 +0200 [thread overview]
Message-ID: <20200331153450.GM30449@dhcp22.suse.cz> (raw)
In-Reply-To: <20200331145806.GB236678@google.com>
On Tue 31-03-20 10:58:06, Joel Fernandes wrote:
[...]
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 4be763355c9fb..965deefffdd58 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -3149,7 +3149,7 @@ static inline struct rcu_head *attach_rcu_head_to_object(void *obj)
> >
> > if (!ptr)
> > ptr = kmalloc(sizeof(unsigned long *) +
> > - sizeof(struct rcu_head), GFP_ATOMIC | __GFP_NOWARN);
> > + sizeof(struct rcu_head), GFP_MEMALLOC);
>
> Just to add, the main requirements here are:
> 1. Allocation should be bounded in time.
> 2. Allocation should try hard (possibly tapping into reserves)
> 3. Sleeping is Ok but should not affect the time bound.
__GFP_ATOMIC | __GFP_HIGH is the way to get an additional access to
memory reserves regarless of the sleeping status.
Using __GFP_MEMALLOC is quite dangerous because it can deplete _all_ the
memory. What does prevent the above code path to do that?
If a partial access to reserves is sufficient then why the existing
modifiers (mentioned above are not sufficient?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-03-31 15:34 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-31 13:16 [PATCH RFC] rcu/tree: Use GFP_MEMALLOC for alloc memory to free memory pattern Joel Fernandes (Google)
2020-03-31 14:04 ` Uladzislau Rezki
2020-03-31 15:09 ` Joel Fernandes
2020-03-31 16:01 ` Uladzislau Rezki
2020-03-31 17:02 ` Uladzislau Rezki
2020-03-31 17:49 ` Paul E. McKenney
2020-03-31 18:30 ` Joel Fernandes
2020-04-01 12:25 ` Uladzislau Rezki
2020-04-01 13:47 ` Paul E. McKenney
2020-04-01 18:16 ` Uladzislau Rezki
2020-04-01 18:26 ` Paul E. McKenney
2020-04-01 18:37 ` Uladzislau Rezki
2020-04-01 18:54 ` Paul E. McKenney
2020-04-01 19:05 ` Uladzislau Rezki
2020-04-01 19:34 ` Paul E. McKenney
2020-04-01 19:35 ` Uladzislau Rezki
2020-03-31 14:58 ` Joel Fernandes
2020-03-31 15:34 ` Michal Hocko [this message]
2020-03-31 16:01 ` Joel Fernandes
2020-03-31 22:19 ` NeilBrown
2020-04-01 3:25 ` Joel Fernandes
2020-04-01 4:52 ` NeilBrown
2020-04-01 7:23 ` Michal Hocko
2020-04-01 11:14 ` joel
2020-04-01 12:05 ` Michal Hocko
2020-04-01 13:14 ` Mel Gorman
2020-04-01 14:45 ` Joel Fernandes
2020-03-31 16:12 ` Uladzislau Rezki
2020-04-01 7:09 ` Michal Hocko
2020-04-01 12:32 ` Uladzislau Rezki
2020-04-01 12:55 ` Michal Hocko
2020-04-01 13:08 ` Uladzislau Rezki
2020-04-01 13:15 ` Michal Hocko
2020-04-01 13:22 ` Uladzislau Rezki
2020-04-01 15:28 ` Michal Hocko
2020-04-01 15:46 ` Uladzislau Rezki
2020-04-01 15:57 ` Paul E. McKenney
2020-04-01 16:10 ` Michal Hocko
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