From: Marcelo Tosatti <mtosatti@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt-users@vger.kernel.org,
Juri Lelli <juri.lelli@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <frederic@kernel.org>
Subject: Re: [patch 2/2] mm: page_alloc: drain pages remotely
Date: Tue, 16 Jun 2020 14:04:25 -0300 [thread overview]
Message-ID: <20200616170425.GA324900@fuller.cnet> (raw)
In-Reply-To: <20200616163248.z5bdrx7gj2sf7d3m@linutronix.de>
On Tue, Jun 16, 2020 at 06:32:48PM +0200, Sebastian Andrzej Siewior wrote:
> On 2020-06-16 13:11:51 [-0300], Marcelo Tosatti wrote:
> > Remote draining of pages was removed from 5.6-rt.
> >
> > Unfortunately its necessary for use-cases which have a busy spinning
> > SCHED_FIFO thread on isolated CPU:
> >
> > [ 7475.821066] INFO: task ld:274531 blocked for more than 600 seconds.
> > [ 7475.822157] Not tainted 4.18.0-208.rt5.20.el8.x86_64 #1
> > [ 7475.823094] echo 0 /proc/sys/kernel/hung_task_timeout_secs disables this message.
> > [ 7475.824392] ld D 0 274531 274530 0x00084080
> > [ 7475.825307] Call Trace:
> > [ 7475.825761] __schedule+0x342/0x850
> > [ 7475.826377] schedule+0x39/0xd0
> > [ 7475.826923] schedule_timeout+0x20e/0x410
> > [ 7475.827610] ? __schedule+0x34a/0x850
> > [ 7475.828247] ? ___preempt_schedule+0x16/0x18
> > [ 7475.828953] wait_for_completion+0x85/0xe0
> > [ 7475.829653] flush_work+0x11a/0x1c0
> > [ 7475.830313] ? flush_workqueue_prep_pwqs+0x130/0x130
> > [ 7475.831148] drain_all_pages+0x140/0x190
> > [ 7475.831803] __alloc_pages_slowpath+0x3f8/0xe20
> > [ 7475.832571] ? mem_cgroup_commit_charge+0xcb/0x510
> > [ 7475.833371] __alloc_pages_nodemask+0x1ca/0x2b0
> > [ 7475.834134] pagecache_get_page+0xb5/0x2d0
> > [ 7475.834814] ? account_page_dirtied+0x11a/0x220
> > [ 7475.835579] grab_cache_page_write_begin+0x1f/0x40
> > [ 7475.836379] iomap_write_begin.constprop.44+0x1c1/0x370
> > [ 7475.837241] ? iomap_write_end+0x91/0x290
> > [ 7475.837911] iomap_write_actor+0x92/0x170
> > ...
> >
> > So enable remote draining again.
>
> Is upstream affected by this? And if not, why not?
It is affected. The workqueue thread for a given CPU is SCHED_OTHER, which can't
interrupt a SCHED_FIFO task which does not sleep.
next prev parent reply other threads:[~2020-06-16 17:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-16 16:11 [patch 0/2] re-enable remote per-cpu-pages draining Marcelo Tosatti
2020-06-16 16:11 ` [patch 1/2] rt: add local_lock_on and local_lock_irqsave_on to locallock.h Marcelo Tosatti
2020-06-16 16:11 ` [patch 2/2] mm: page_alloc: drain pages remotely Marcelo Tosatti
2020-06-16 16:32 ` Sebastian Andrzej Siewior
2020-06-16 16:55 ` Marcelo Tosatti
2020-06-17 7:42 ` Sebastian Andrzej Siewior
2020-06-17 10:11 ` Marcelo Tosatti
2020-06-17 12:01 ` Sebastian Andrzej Siewior
2020-06-16 17:04 ` Marcelo Tosatti [this message]
2020-06-17 7:46 ` Sebastian Andrzej Siewior
2020-06-17 10:12 ` Marcelo Tosatti
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