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From: Uladzislau Rezki <urezki@gmail.com>
To: Michal Hocko <mhocko@suse.com>, "Paul E. McKenney" <paulmck@kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
	rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	mgorman@techsingularity.net, torvalds@linux-foundation.org,
	"Uladzislau Rezki (Sony)" <urezki@gmail.com>
Subject: Re: [PATCH tip/core/rcu 14/15] rcu/tree: Allocate a page when caller is preemptible
Date: Wed, 30 Sep 2020 14:31:53 +0200	[thread overview]
Message-ID: <20200930123153.GA18005@pc636> (raw)
In-Reply-To: <20200930084139.GN2277@dhcp22.suse.cz>

>
> > > What is the point of calling kmalloc  for a PAGE_SIZE object? Wouldn't
> > > using the page allocator directly be better?
> > 
> > Well, you guys gave me considerable heat about abusing internal allocator
> > interfaces, and kmalloc() and kfree() seem to be about as non-internal
> > as you can get and still be invoking the allocator.  ;-)
> 
> alloc_pages resp. __get_free_pages is a normal page allocator interface
> to use for page size granular allocations. kmalloc is for more fine
> grained allocations.
>
I do not have a strong opinion here but i would tend to using of the page
allocator directly. Because we operate on a page level where the page
allocator is supposed to be used. From the other hand i saw a slightly
better performance in case of SLAB only. I think that is because of
a) slab caches; b) more objects which can be cached. But i have one more
concern about using of kmalloc(). That is about fragmentations it can
cause with PAGE_SIZE requests.

As for SLUB it was identical whereas the SLOB i din not check.

--
Vlad Rezki

  reply	other threads:[~2020-09-30 12:31 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-28 23:30 [PATCH tip/core/rcu 0/15] Paul E. McKenney
2020-09-28 23:30 ` [PATCH tip/core/rcu 01/15] lib/debug: Remove pointless ARCH_NO_PREEMPT dependencies paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 02/15] preempt: Make preempt count unconditional paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 03/15] preempt: Cleanup PREEMPT_COUNT leftovers paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 04/15] lockdep: " paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 05/15] mm/pagemap: " paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 06/15] locking/bitspinlock: " paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 07/15] uaccess: " paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 08/15] sched: " paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 09/15] ARM: " paulmck
2020-09-28 23:30   ` paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 10/15] xtensa: " paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 11/15] drm/i915: " paulmck
2020-09-28 23:30   ` [Intel-gfx] " paulmck
2020-09-28 23:30   ` paulmck
2020-10-01  7:17   ` Joonas Lahtinen
2020-10-01  7:17     ` [Intel-gfx] " Joonas Lahtinen
2020-10-01  7:17     ` Joonas Lahtinen
2020-10-01  8:25     ` Thomas Gleixner
2020-10-01  8:25       ` [Intel-gfx] " Thomas Gleixner
2020-10-01  8:25       ` Thomas Gleixner
2020-10-01 16:03       ` Paul E. McKenney
2020-10-01 16:03         ` [Intel-gfx] " Paul E. McKenney
2020-10-01 16:03         ` Paul E. McKenney
2020-09-28 23:30 ` [PATCH tip/core/rcu 12/15] rcutorture: " paulmck
2020-09-28 23:31 ` [PATCH tip/core/rcu 13/15] preempt: Remove PREEMPT_COUNT from Kconfig paulmck
2020-09-28 23:31 ` [PATCH tip/core/rcu 14/15] rcu/tree: Allocate a page when caller is preemptible paulmck
2020-09-29 12:07   ` Michal Hocko
2020-09-30  1:53     ` Paul E. McKenney
2020-09-30  8:41       ` Michal Hocko
2020-09-30 12:31         ` Uladzislau Rezki [this message]
2020-09-30 23:21         ` Paul E. McKenney
2020-10-01  9:02           ` Michal Hocko
2020-10-01 16:27             ` Paul E. McKenney
2020-10-02  6:57               ` Michal Hocko
2020-10-02 14:12                 ` Paul E. McKenney
2020-10-01 16:28             ` Paul E. McKenney
2020-10-01 20:03             ` Uladzislau Rezki
2020-09-28 23:31 ` [PATCH tip/core/rcu 15/15] kvfree_rcu(): Fix ifnullfree.cocci warnings paulmck

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