From: Daniel Wagner <dwagner@suse.de>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
"Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Hillf Danton <hdanton@sina.com>, Michal Hocko <mhocko@suse.com>,
Matthew Wilcox <willy@infradead.org>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v2 1/1] mm/vmalloc: remove preempt_disable/enable when do preloading
Date: Fri, 11 Oct 2019 23:56:42 +0200 [thread overview]
Message-ID: <c5b522c3-2d38-a8c8-b9e9-b3e3448ed8fa@suse.de> (raw)
In-Reply-To: <20191011181532.nardqmokz7yxtsu3@linutronix.de>
On 10/11/19 8:15 PM, Sebastian Andrzej Siewior wrote:
> On 2019-10-11 00:33:18 [+0200], Uladzislau Rezki (Sony) wrote:
>> Get rid of preempt_disable() and preempt_enable() when the
>> preload is done for splitting purpose. The reason is that
>> calling spin_lock() with disabled preemtion is forbidden in
>> CONFIG_PREEMPT_RT kernel.
>>
>> Therefore, we do not guarantee that a CPU is preloaded, instead
>> we minimize the case when it is not with this change.
>>
>> For example i run the special test case that follows the preload
>> pattern and path. 20 "unbind" threads run it and each does
>> 1000000 allocations. Only 3.5 times among 1000000 a CPU was
>> not preloaded. So it can happen but the number is negligible.
>>
>> V1 -> V2:
>> - move __this_cpu_cmpxchg check when spin_lock is taken,
>> as proposed by Andrew Morton
>> - add more explanation in regard of preloading
>> - adjust and move some comments
>>
>> Fixes: 82dd23e84be3 ("mm/vmalloc.c: preload a CPU with one object for split purpose")
>> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
>> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
>
> Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Daniel Wagner <dwagner@suse.de>
next prev parent reply other threads:[~2019-10-11 21:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-10 22:33 [PATCH v2 1/1] mm/vmalloc: remove preempt_disable/enable when do preloading Uladzislau Rezki (Sony)
2019-10-11 18:15 ` Sebastian Andrzej Siewior
2019-10-11 21:56 ` Daniel Wagner [this message]
2019-10-14 13:13 ` Michal Hocko
2019-10-14 14:30 ` Uladzislau Rezki
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