From: Uladzislau Rezki <urezki@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Uladzislau Rezki <urezki@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
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: Wed, 1 Apr 2020 17:46:18 +0200 [thread overview]
Message-ID: <20200401154618.GA3907@pc636> (raw)
In-Reply-To: <20200401152805.GN22681@dhcp22.suse.cz>
> > >
> > > OK, if you are always in the atomic context then GFP_ATOMIC is
> > > sufficient. __GFP_RETRY_MAYFAIL will make no difference for allocations
> > > which do not reclaim (and thus not retry). Sorry this was not clear to
> > > me from the previous description.
> > >
> > Ahh. OK. Then adding __GFP_RETRY_MAYFAIL to GFP_ATOMIC will not make any effect.
> >
> > Thank you for your explanation!
>
> Welcome. I wish all those gfp flags were really clear but I fully
> understand that people who are not working with MM regurarly might find
> it confusing. Btw. have __GFP_RETRY_MAYFAIL is documented in gfp.h and
> it is documented as the reclaim modifier which should imply that it has
> no effect when the reclaim is not allowed which is the case for any non
> sleeping allocation. If that relation was not immediately obvious then I
> think we need to make it explicit. Would you find it useful?
>
> E.g.
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index e3ab1c0d9140..8f09cefdfa7b 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -127,6 +127,8 @@ struct vm_area_struct;
> *
> * Reclaim modifiers
> * ~~~~~~~~~~~~~~~~~
> + * Please note that all the folloging flags are only applicable to sleepable
> + * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them).
> *
> * %__GFP_IO can start physical IO.
> *
That would be definitely clear for me!
--
Vlad Rezki
next prev parent reply other threads:[~2020-04-01 15:46 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
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 [this message]
2020-04-01 15:57 ` Paul E. McKenney
2020-04-01 16:10 ` Michal Hocko
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