From: Andi Kleen <ak@linux.intel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Uros Bizjak <ubizjak@gmail.com>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>
Subject: Re: [RFC PATCH, x86]: Disable CPA cache flush for selfsnoop targets
Date: Mon, 15 Jul 2019 17:32:22 -0700 [thread overview]
Message-ID: <20190716003222.GJ32439@tassilo.jf.intel.com> (raw)
In-Reply-To: <CALCETrW8yTRyP3qnOv04B2XvR5ZHDUky15CCBR2gtNVG3bea-Q@mail.gmail.com>
On Mon, Jul 15, 2019 at 04:10:36PM -0700, Andy Lutomirski wrote:
> On Mon, Jul 15, 2019 at 3:53 PM Andi Kleen <ak@linux.intel.com> wrote:
> >
> > > I haven't tested on a real kernel with i915. Does i915 really hit
> > > this code path? Does it happen more than once or twice at boot?
> >
> > Yes some workloads allocate/free a lot of write combined memory
> > for graphics objects.
> >
>
> But where does that memory come from? If it's from device memory
> (i.e. memory that's not in the kernel direct map), then, unless I
> missed something, we're never changing the cache mode per se -- we're
> just ioremap_wc-ing it, which doesn't require a flush.
Integraded graphics doesn't have device memory. There's an reserved
memory area, but a lot of the buffers the GPU works with
come from main memory.
-Andi
next prev parent reply other threads:[~2019-07-16 0:32 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-11 8:12 [RFC PATCH, x86]: Disable CPA cache flush for selfsnoop targets Uros Bizjak
2019-07-11 14:39 ` Andy Lutomirski
2019-07-11 19:00 ` Uros Bizjak
2019-07-15 8:24 ` Thomas Gleixner
2019-07-15 12:04 ` Uros Bizjak
2019-07-15 16:31 ` Andi Kleen
2019-07-15 18:41 ` Thomas Gleixner
2019-07-15 19:19 ` Uros Bizjak
2019-07-15 19:30 ` Thomas Gleixner
2019-07-15 19:38 ` Andi Kleen
2019-07-15 22:12 ` Andy Lutomirski
2019-07-15 22:53 ` Andi Kleen
2019-07-15 23:10 ` Andy Lutomirski
2019-07-16 0:32 ` Andi Kleen [this message]
2019-07-15 19:39 ` Andi Kleen
2019-07-15 19:44 ` Andy Lutomirski
2019-07-15 19:46 ` Thomas Gleixner
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