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From: Thomas Gleixner <tglx@linutronix.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
	Jeff Moyer <jmoyer@redhat.com>,
	linux-nvdimm <linux-nvdimm@ml01.01.org>, X86 ML <x86@kernel.org>,
	Dave Chinner <david@fromorbit.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Jan Kara <jack@suse.com>
Subject: Re: [PATCH 0/2] "big hammer" for DAX msync/fsync correctness
Date: Fri, 6 Nov 2015 18:35:11 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.11.1511061832590.4032@nanos> (raw)
In-Reply-To: <CAPcyv4jJ3f=HC7p08KQwH4Q0+JzwqYJ8tw43j=7f8zSfOjpO2w@mail.gmail.com>

On Fri, 6 Nov 2015, Dan Williams wrote:
> On Fri, Nov 6, 2015 at 12:06 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > Just for the record. Such a flush mechanism with
> >
> >      on_each_cpu()
> >         wbinvd()
> >         ...
> >
> > will make that stuff completely unusable on Real-Time systems. We've
> > been there with the big hammer approach of the intel graphics
> > driver.
> 
> Noted.  This means RT systems either need to disable DAX or avoid
> fsync.  Yes, this is a wart, but not an unexpected one in a first
> generation persistent memory platform.

And it's not just only RT. The folks who are aiming for 100%
undisturbed user space (NOHZ_FULL) will be massively unhappy about
that as well.

Is it really required to do that on all cpus?

Thanks,

	tglx

  reply	other threads:[~2015-11-06 17:36 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-28 22:09 Ross Zwisler
2015-10-28 22:09 ` [PATCH 1/2] pmem: add wb_cache_pmem() to the PMEM API Ross Zwisler
2015-10-28 22:09 ` [PATCH 2/2] pmem: Add simple and slow fsync/msync support Ross Zwisler
2015-10-28 23:02   ` Dan Williams
2015-10-28 22:24 ` [PATCH 0/2] "big hammer" for DAX msync/fsync correctness Jeff Moyer
2015-10-28 22:49   ` Dan Williams
2015-10-28 22:51   ` Ross Zwisler
2015-11-05 23:59     ` Dan Williams
2015-11-06  8:06       ` Thomas Gleixner
2015-11-06 16:04         ` Dan Williams
2015-11-06 17:35           ` Thomas Gleixner [this message]
2015-11-06 23:17             ` Dan Williams
2015-11-07  0:51               ` H. Peter Anvin
2015-11-07  6:50                 ` Thomas Gleixner
2015-11-07  8:12                   ` Dan Williams
2015-11-07  8:38                     ` Thomas Gleixner
2015-11-07  9:02                       ` Dan Williams
2015-11-07  9:24                         ` Thomas Gleixner
2015-11-06 20:25       ` H. Peter Anvin

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