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From: Christoph Lameter <cl@gentwo.de>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Pekka Enberg <penberg@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org
Subject: Re: [PATCH 1/9] slub: Make PREEMPT_RT support less convoluted
Date: Thu, 18 Aug 2022 11:42:00 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.22.394.2208181136560.1901102@gentwo.de> (raw)
In-Reply-To: <20220817162703.728679-2-bigeasy@linutronix.de>

On Wed, 17 Aug 2022, Sebastian Andrzej Siewior wrote:

> + *   On PREEMPT_RT, the local lock neither disables interrupts nor preemption
> + *   which means the lockless fastpath cannot be used as it might interfere with
> + *   an in-progress slow path operations. In this case the local lock is always
> + *   taken but it still utilizes the freelist for the common operations.

The slub fastpath does not interfere with slow path operations and the
fastpath does not require disabling preemption or interrupts if the
processor supports local rmv operations. So you should be able to use the
fastpath on PREEMPT_RT.

If the fastpath is not possible then you need to disable preemption and
eventually take locks etc and then things may get a bit more complicated.



  reply	other threads:[~2022-08-18  9:42 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-17 16:26 [PATCH 0/9] Replace PREEMPT_RT ifdefs with preempt_[dis|en]able_nested() Sebastian Andrzej Siewior
2022-08-17 16:26 ` [PATCH 1/9] slub: Make PREEMPT_RT support less convoluted Sebastian Andrzej Siewior
2022-08-18  9:42   ` Christoph Lameter [this message]
2022-08-18 14:37     ` Vlastimil Babka
2022-08-18 15:22       ` Sebastian Andrzej Siewior
2022-08-19 15:04       ` Christoph Lameter
2022-08-25  5:15         ` Hyeonggon Yoo
2022-08-18 17:34   ` Linus Torvalds
2022-08-23 17:15   ` Vlastimil Babka
2022-08-24 13:25     ` Sebastian Andrzej Siewior
2022-08-24 13:54       ` Vlastimil Babka
2022-08-24 13:57         ` Sebastian Andrzej Siewior
2022-08-17 16:26 ` [PATCH 2/9] preempt: Provide preempt_[dis|en]able_nested() Sebastian Andrzej Siewior
2022-08-17 16:26 ` [PATCH 3/9] dentry: Use preempt_[dis|en]able_nested() Sebastian Andrzej Siewior
2022-08-17 16:26 ` [PATCH 4/9] mm/vmstat: " Sebastian Andrzej Siewior
2022-08-17 16:26 ` [PATCH 5/9] mm/debug: Provide VM_WARN_ON_IRQS_ENABLED() Sebastian Andrzej Siewior
2022-08-17 16:27 ` [PATCH 6/9] mm/memcontrol: Replace the PREEMPT_RT conditionals Sebastian Andrzej Siewior
2022-08-17 16:27   ` Sebastian Andrzej Siewior
2022-08-17 16:59   ` Johannes Weiner
2022-08-17 16:59     ` Johannes Weiner
2022-08-18  2:45   ` Muchun Song
2022-08-18  2:45     ` Muchun Song
2022-08-17 16:27 ` [PATCH 7/9] mm/compaction: Get rid of RT ifdeffery Sebastian Andrzej Siewior
2022-08-18  8:55   ` Rasmus Villemoes
2022-08-18 15:51     ` Sebastian Andrzej Siewior
2022-08-24 13:50     ` Thomas Gleixner
2022-08-17 16:27 ` [PATCH 8/9] u64_stats: Streamline the implementation Sebastian Andrzej Siewior
2022-08-17 16:27 ` [PATCH 9/9] u64_stat: Remove the obsolete fetch_irq() variants Sebastian Andrzej Siewior
2022-08-17 18:27   ` Jakub Kicinski
2022-08-18 15:27     ` Sebastian Andrzej Siewior
2022-08-18 16:02       ` Jakub Kicinski
2022-08-18 16:59         ` Sebastian Andrzej Siewior
2022-08-18 17:45           ` Jakub Kicinski
2022-08-22 15:17             ` Sebastian Andrzej Siewior
2022-08-22 18:05               ` Jakub Kicinski
2022-08-25 16:45                 ` Sebastian Andrzej Siewior
2022-08-25 17:30                   ` Jakub Kicinski
2022-08-18  8:20 ` [PATCH 0/9] Replace PREEMPT_RT ifdefs with preempt_[dis|en]able_nested() Peter Zijlstra
2022-08-18 17:41 ` Linus Torvalds

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