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From: Michal Hocko <mhocko@suse.com>
To: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	Daniel Axtens <dja@axtens.net>,
	Frederic Weisbecker <frederic@kernel.org>,
	Neeraj Upadhyay <neeraju@codeaurora.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Theodore Y . Ts'o" <tytso@mit.edu>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Subject: Re: [PATCH 1/3] kvfree_rcu: Allocate a page for a single argument
Date: Mon, 25 Jan 2021 14:22:36 +0100	[thread overview]
Message-ID: <20210125132236.GJ827@dhcp22.suse.cz> (raw)
In-Reply-To: <20210120162148.1973-1-urezki@gmail.com>

On Wed 20-01-21 17:21:46, Uladzislau Rezki (Sony) wrote:
> For a single argument we can directly request a page from a caller
> context when a "carry page block" is run out of free spots. Instead
> of hitting a slow path we can request an extra page by demand and
> proceed with a fast path.
> 
> A single-argument kvfree_rcu() must be invoked in sleepable contexts,
> and that its fallback is the relatively high latency synchronize_rcu().
> Single-argument kvfree_rcu() therefore uses GFP_KERNEL|__GFP_RETRY_MAYFAIL
> to allow limited sleeping within the memory allocator.

__GFP_RETRY_MAYFAIL can be quite heavy. It is effectively the most heavy
way to allocate without triggering the OOM killer. Is this really what
you need/want? Is __GFP_NORETRY too weak?

-- 
Michal Hocko
SUSE Labs

  parent reply	other threads:[~2021-01-25 13:29 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-20 16:21 [PATCH 1/3] kvfree_rcu: Allocate a page for a single argument Uladzislau Rezki (Sony)
2021-01-20 16:21 ` [PATCH 2/3] kvfree_rcu: Use __GFP_NOMEMALLOC for single-argument kvfree_rcu() Uladzislau Rezki (Sony)
2021-01-28 18:06   ` Uladzislau Rezki
2021-01-20 16:21 ` [PATCH 3/3] kvfree_rcu: use migrate_disable/enable() Uladzislau Rezki (Sony)
2021-01-20 19:45   ` Sebastian Andrzej Siewior
2021-01-20 21:42     ` Paul E. McKenney
2021-01-23  9:31   ` 回复: " Zhang, Qiang
2021-01-24 21:57     ` Uladzislau Rezki
2021-01-25  1:50       ` 回复: " Zhang, Qiang
2021-01-25  2:18         ` Zhang, Qiang
2021-01-25 13:49           ` Uladzislau Rezki
2021-01-26  9:33             ` 回复: " Zhang, Qiang
2021-01-26 13:43               ` Uladzislau Rezki
2021-01-20 18:40 ` [PATCH 1/3] kvfree_rcu: Allocate a page for a single argument Paul E. McKenney
2021-01-20 19:57 ` Sebastian Andrzej Siewior
2021-01-20 21:54   ` Paul E. McKenney
2021-01-21 13:35     ` Uladzislau Rezki
2021-01-21 15:07       ` Paul E. McKenney
2021-01-21 19:17         ` Uladzislau Rezki
2021-01-22 11:17     ` Sebastian Andrzej Siewior
2021-01-22 15:28       ` Paul E. McKenney
2021-01-21 12:38   ` Uladzislau Rezki
2021-01-22 11:34     ` Sebastian Andrzej Siewior
2021-01-22 14:21       ` Uladzislau Rezki
2021-01-25 13:22 ` Michal Hocko [this message]
2021-01-25 14:31   ` Uladzislau Rezki
2021-01-25 15:39     ` Michal Hocko
2021-01-25 16:25       ` Uladzislau Rezki
2021-01-28 15:11         ` Uladzislau Rezki
2021-01-28 15:17           ` Michal Hocko
2021-01-28 15:30             ` Uladzislau Rezki
2021-01-28 18:02               ` Uladzislau Rezki
     [not found]                 ` <YBPNvbJLg56XU8co@dhcp22.suse.cz>
2021-01-29 16:35                   ` Uladzislau Rezki
2021-02-01 11:47                     ` Michal Hocko
2021-02-01 14:44                       ` Uladzislau Rezki
2021-02-03 19:37                       ` Paul E. McKenney

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