From: Uladzislau Rezki <urezki@gmail.com>
To: Michal Hocko <mhocko@suse.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>,
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 15:31:50 +0100 [thread overview]
Message-ID: <20210125143150.GA2282@pc638.lan> (raw)
In-Reply-To: <20210125132236.GJ827@dhcp22.suse.cz>
> 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?
>
Hm... We agreed to proceed with limited lightwait memory direct reclaim.
Johannes Weiner proposed to go with __GFP_NORETRY flag as a starting
point: https://www.spinics.net/lists/rcu/msg02856.html
<snip>
So I'm inclined to suggest __GFP_NORETRY as a starting point, and make
further decisions based on instrumentation of the success rates of
these opportunistic allocations.
<snip>
but for some reason, i can't find a tail or head of it, we introduced
__GFP_RETRY_MAYFAIL what is a heavy one from a time consuming point of view.
What we would like to avoid.
I tend to say that it was a typo.
Thank you for pointing to it!
--
Vlad Rezki
next prev parent reply other threads:[~2021-01-25 14:34 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
2021-01-25 14:31 ` Uladzislau Rezki [this message]
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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