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From: Uladzislau Rezki <urezki@gmail.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Uladzislau Rezki <urezki@gmail.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Theodore Y . Ts'o" <tytso@mit.edu>,
	Joel Fernandes <joel@joelfernandes.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>,
	Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [RFC-PATCH 2/4] mm: Add __rcu_alloc_page_lockless() func.
Date: Mon, 5 Oct 2020 15:58:54 +0200	[thread overview]
Message-ID: <20201005135854.GA17959@pc636> (raw)
In-Reply-To: <20201002071123.GB20872@dhcp22.suse.cz>

On Fri, Oct 02, 2020 at 09:11:23AM +0200, Michal Hocko wrote:
> On Thu 01-10-20 21:26:26, Uladzislau Rezki wrote:
> > > 
> > > No, I meant going back to idea of new gfp flag, but adjust the implementation in
> > > the allocator (different from what you posted in previous version) so that it
> > > only looks at the flag after it tries to allocate from pcplist and finds out
> > > it's empty. So, no inventing of new page allocator entry points or checks such
> > > as the one you wrote above, but adding the new gfp flag in a way that it doesn't
> > > affect existing fast paths.
> > >
> > OK. Now i see. Please have a look below at the patch, so we fully understand
> > each other. If that is something that is close to your view or not:
> > 
> > <snip>
> > t a/include/linux/gfp.h b/include/linux/gfp.h
> > index c603237e006c..7e613560a502 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -39,8 +39,9 @@ struct vm_area_struct;
> >  #define ___GFP_HARDWALL                0x100000u
> >  #define ___GFP_THISNODE                0x200000u
> >  #define ___GFP_ACCOUNT         0x400000u
> > +#define ___GFP_NO_LOCKS                0x800000u
> 
> Even if a new gfp flag gains a sufficient traction and support I am
> _strongly_ opposed against consuming another flag for that. Bit space is
> limited.
>
That is a valid point.

>
> Besides that we certainly do not want to allow craziness like
> __GFP_NO_LOCK | __GFP_RECLAIM (and similar), do we?
>
Obviously not. And it seems that the way of implementing of the
NO_LOCK logic would be easier(less code changes) and better if
it was defined like below(what you proposed later in this thread):

-#define __GFP_NO_LOCKS ((__force gfp_t)___GFP_NO_LOCKS)
+#define __GFP_NO_LOCKS ((__force gfp_t) 0)

That could imply that calling the page allocator with zero
argument would apply a further limitation - that is lock free.

--
Vlad Rezki

  parent reply	other threads:[~2020-10-05 13:59 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-18 19:48 [PATCH 0/4] kvfree_rcu() and _LOCK_NESTING/_PREEMPT_RT Uladzislau Rezki (Sony)
2020-09-18 19:48 ` [PATCH 1/4] rcu/tree: Add a work to allocate pages from regular context Uladzislau Rezki (Sony)
2020-09-18 19:48 ` [RFC-PATCH 2/4] mm: Add __rcu_alloc_page_lockless() func Uladzislau Rezki (Sony)
2020-09-21  7:47   ` Michal Hocko
2020-09-21 15:45     ` Paul E. McKenney
2020-09-21 16:03       ` Michal Hocko
2020-09-21 19:48         ` Uladzislau Rezki
2020-09-22  7:50           ` Michal Hocko
2020-09-22 13:12             ` Uladzislau Rezki
2020-09-22 15:35               ` Michal Hocko
2020-09-23 10:37               ` Mel Gorman
2020-09-23 15:41                 ` Paul E. McKenney
2020-09-23 23:22                   ` Mel Gorman
2020-09-24  8:16                     ` Uladzislau Rezki
2020-09-24 11:16                       ` Peter Zijlstra
2020-09-24 15:16                         ` Uladzislau Rezki
2020-09-24 11:19                       ` Peter Zijlstra
2020-09-24 15:21                         ` Uladzislau Rezki
2020-09-25  8:15                           ` Peter Zijlstra
2020-09-25 10:25                             ` Uladzislau Rezki
2020-09-24 15:38                         ` Paul E. McKenney
2020-09-25  8:26                           ` Peter Zijlstra
2020-09-26 14:37                             ` Paul E. McKenney
2020-09-25  8:05                       ` Michal Hocko
2020-09-25 15:31                         ` Uladzislau Rezki
2020-09-25 15:47                           ` Michal Hocko
2020-09-29 16:25                             ` Uladzislau Rezki
2020-09-30  9:27                               ` Michal Hocko
2020-09-30 12:35                                 ` Uladzislau Rezki
2020-09-30 12:44                                   ` Michal Hocko
2020-09-30 13:39                                     ` Uladzislau Rezki
2020-09-30 16:46                                       ` Michal Hocko
2020-09-30 20:36                                         ` Uladzislau Rezki
2020-09-30 15:25                             ` Joel Fernandes
2020-09-30 16:48                               ` Michal Hocko
2020-09-30 17:03                                 ` Joel Fernandes
2020-09-30 17:03                                   ` Joel Fernandes
2020-09-30 17:22                                   ` Michal Hocko
2020-09-30 17:48                                     ` Joel Fernandes
2020-09-30 17:48                                       ` Joel Fernandes
2020-09-25 16:17                           ` Mel Gorman
2020-09-25 17:57                             ` Uladzislau Rezki
2020-09-22 15:49             ` Paul E. McKenney
2020-09-22  3:35         ` Paul E. McKenney
2020-09-22  8:03           ` Michal Hocko
2020-09-22 15:46             ` Paul E. McKenney
2020-09-23 11:27               ` Uladzislau Rezki
2020-09-29 10:15   ` Vlastimil Babka
2020-09-29 22:07     ` Uladzislau Rezki
2020-09-30 10:35       ` Michal Hocko
2020-10-01 19:32         ` Uladzislau Rezki
2020-09-30 14:39       ` Vlastimil Babka
2020-09-30 15:37         ` Joel Fernandes
2020-10-01 19:26         ` Uladzislau Rezki
2020-10-02  7:11           ` Michal Hocko
2020-10-02  8:50             ` Mel Gorman
2020-10-02  9:05               ` Michal Hocko
2020-10-05 15:08                 ` Uladzislau Rezki
2020-10-05 15:41                   ` Michal Hocko
2020-10-06 22:25                     ` Uladzislau Rezki
2020-10-07 10:02                       ` Michal Hocko
2020-10-07 11:02                         ` Uladzislau Rezki
2020-10-02  9:07               ` Peter Zijlstra
2020-10-02  9:45                 ` Mel Gorman
2020-10-02  9:58                   ` Peter Zijlstra
2020-10-02 10:19                     ` Mel Gorman
2020-10-02 14:41                       ` Paul E. McKenney
2020-10-06 10:03                         ` Mel Gorman
2020-10-06 15:41                           ` Paul E. McKenney
2020-10-05 13:58             ` Uladzislau Rezki [this message]
2020-10-02  8:06           ` Mel Gorman
2020-10-05 14:12             ` Uladzislau Rezki
2020-09-18 19:48 ` [PATCH 3/4] rcu/tree: use " Uladzislau Rezki (Sony)
2020-09-18 19:48 ` [PATCH 4/4] rcu/tree: Use schedule_delayed_work() instead of WQ_HIGHPRI queue Uladzislau Rezki (Sony)
2020-09-20 15:06   ` Paul E. McKenney
2020-09-21 13:27     ` Uladzislau Rezki
2020-09-18 22:15 ` [PATCH 0/4] kvfree_rcu() and _LOCK_NESTING/_PREEMPT_RT Paul E. McKenney
2020-09-30 15:52 ` Joel Fernandes

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