From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
eranian@google.com, tglx@linutronix.de,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation
Date: Wed, 10 Sep 2014 18:58:48 +0200 [thread overview]
Message-ID: <20140910165848.GA11901@worktop.ger.corp.intel.com> (raw)
In-Reply-To: <20140910163556.GE4783@worktop.ger.corp.intel.com>
On Wed, Sep 10, 2014 at 06:35:56PM +0200, Peter Zijlstra wrote:
> On Wed, Sep 10, 2014 at 04:40:12PM +0200, Andi Kleen wrote:
> > > We did this once, and that blew up big time.
> > >
> > > Even now, vmalloc_fault() has a very explicit:
> > >
> > > WARN_ON_ONCE(in_nmi());
> > >
> > > So this isn't going to happen until you fix that.
> >
> > Good point.
> >
> > We just need to call vmalloc_sync_all at allocation time,
> > no need to change vmalloc_fault.
>
> Somehow that wasn't considered adequate, but lemme try and dig out that
> thread. It should be somewhere...
>
> https://lkml.org/lkml/2010/7/14/465
Note that since then we have actually fixed the 'cannot fault from NMI
context' thing, so we should be able to actually take those faults. I
suspect we can simply remove those WARNs from the vmalloc fault path,
but it would need double checking to see if there's no other reasons.
Also:
https://lkml.org/lkml/2014/4/10/581
https://patchwork.kernel.org/patch/3048111/
I'm not entirely sure what the final conclusion is, except to note that
it didn't happen.
next prev parent reply other threads:[~2014-09-10 16:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-10 0:03 [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation Andi Kleen
2014-09-10 7:57 ` Peter Zijlstra
2014-09-10 14:40 ` Andi Kleen
2014-09-10 16:35 ` Peter Zijlstra
2014-09-10 16:58 ` Peter Zijlstra [this message]
2014-09-10 18:27 ` Andi Kleen
2014-09-10 18:52 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140910165848.GA11901@worktop.ger.corp.intel.com \
--to=peterz@infradead.org \
--cc=ak@linux.intel.com \
--cc=andi@firstfloor.org \
--cc=eranian@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox