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From: Frederic Weisbecker <frederic@kernel.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: linux-kernel@vger.kernel.org, Nitesh Lal <nilal@redhat.com>,
	Nicolas Saenz Julienne <nsaenzju@redhat.com>,
	Christoph Lameter <cl@linux.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Alex Belits <abelits@belits.com>, Peter Xu <peterx@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Oscar Shiang <oscar0225@livemail.tw>
Subject: Re: [patch v11 07/13] task isolation: sync vmstats conditional on changes
Date: Mon, 7 Feb 2022 16:29:43 +0100	[thread overview]
Message-ID: <20220207152943.GB526112@lothringen> (raw)
In-Reply-To: <20220204173554.763888172@fedora.localdomain>

On Fri, Feb 04, 2022 at 02:35:44PM -0300, Marcelo Tosatti wrote:
> Rather than syncing VM-stats on every return to userspace
> (or VM-entry), keep track of changes through a per-CPU bool.
> 
> This improves performance when enabling task isolated
> for vcpu VMs.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> ---
> v11:
> - Add TIF_TASK_ISOL bit to thread info flags and use it
>   to decide whether to perform task isolation work on
>   return to userspace     
> 
>  include/linux/vmstat.h |   13 ++++++++++++-
>  mm/vmstat.c            |   29 ++++++++++++++++++++++++++++-
>  2 files changed, 40 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6/include/linux/vmstat.h
> ===================================================================
> --- linux-2.6.orig/include/linux/vmstat.h
> +++ linux-2.6/include/linux/vmstat.h
> @@ -22,7 +22,18 @@ int sysctl_vm_numa_stat_handler(struct c
>  #endif
>  
>  #if defined(CONFIG_SMP) && defined(CONFIG_TASK_ISOLATION)
> -void sync_vmstat(void);
> +DECLARE_PER_CPU_ALIGNED(bool, vmstat_dirty);
> +
> +extern struct static_key vmstat_sync_enabled;
> +
> +void __sync_vmstat(void);
> +static inline void sync_vmstat(void)
> +{
> +	if (static_key_false(&vmstat_sync_enabled))
> +		__sync_vmstat();
> +}
> +
> +void init_sync_vmstat(void);
>  #else
>  static inline void sync_vmstat(void)
>  {
> Index: linux-2.6/mm/vmstat.c
> ===================================================================
> --- linux-2.6.orig/mm/vmstat.c
> +++ linux-2.6/mm/vmstat.c
> @@ -334,6 +334,31 @@ void set_pgdat_percpu_threshold(pg_data_
>  	}
>  }
>  
> +#ifdef CONFIG_TASK_ISOLATION
> +struct static_key vmstat_sync_enabled;
> +DEFINE_PER_CPU_ALIGNED(bool, vmstat_dirty);
> +
> +static inline void mark_vmstat_dirty(void)
> +{
> +	if (!static_key_false(&vmstat_sync_enabled))
> +		return;
> +
> +	raw_cpu_write(vmstat_dirty, true);
> +	set_thread_flag(TIF_TASK_ISOL);

This will force the return-to-user slow path on all CPUs,
whether the current task is isolated or not, right?

Also if we context switch to an isolated TASK B with a dirty vmstat,
we miss the TIF_TASK_ISOL.

  parent reply	other threads:[~2022-02-07 15:32 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-04 17:35 [patch v11 00/13] extensible prctl task isolation interface and vmstat sync Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 01/13] s390: add support for TIF_TASK_ISOL Marcelo Tosatti
2022-02-07 11:40   ` Sven Schnelle
2022-02-04 17:35 ` [patch v11 02/13] x86: " Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 03/13] add basic task isolation prctl interface Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 04/13] add prctl task isolation prctl docs and samples Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 05/13] task isolation: sync vmstats on return to userspace Marcelo Tosatti
2022-02-07 14:57   ` Frederic Weisbecker
2022-02-07 15:16     ` Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 06/13] procfs: add per-pid task isolation state Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 07/13] task isolation: sync vmstats conditional on changes Marcelo Tosatti
2022-02-07 15:19   ` Frederic Weisbecker
2022-03-10 16:30     ` Marcelo Tosatti
2022-02-07 15:29   ` Frederic Weisbecker [this message]
2022-02-04 17:35 ` [patch v11 08/13] task isolation: enable return to userspace processing Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 09/13] task isolation: add preempt notifier to sync per-CPU vmstat dirty info to thread info Marcelo Tosatti
2022-02-07 15:36   ` Frederic Weisbecker
2022-02-04 17:35 ` [patch v11 10/13] KVM: x86: process isolation work from VM-entry code path Marcelo Tosatti
2022-02-07 15:47   ` Frederic Weisbecker
2022-03-10 16:35     ` Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 11/13] mm: vmstat: move need_update Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 12/13] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean Marcelo Tosatti
2022-02-04 17:35 ` [patch v11 13/13] task isolation: only TIF_TASK_ISOL if task isolation is enabled Marcelo Tosatti
2022-02-07 15:38   ` Frederic Weisbecker
2022-02-19  8:02 ` [patch v11 00/13] extensible prctl task isolation interface and vmstat sync Oscar Shiang
2022-02-23 17:31   ` Marcelo Tosatti
2022-03-08  6:32     ` Oscar Shiang
2022-03-08 13:12       ` Marcelo Tosatti
2022-03-09 15:31         ` Oscar Shiang
2022-03-08  7:20 ` Oscar Shiang

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