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
next prev parent reply other threads:[~2020-09-30 12:31 UTC|newest]
Thread overview: 30+ 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 ` [PATCH tip/core/rcu 10/15] xtensa: " paulmck
2020-09-28 23:30 ` [PATCH tip/core/rcu 11/15] drm/i915: " paulmck
2020-10-01 7:17 ` Joonas Lahtinen
2020-10-01 8:25 ` Thomas Gleixner
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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