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Date: Mon, 9 Sep 2013 09:36:39 +0530
From: Ramkumar Ramachandra <artagnon@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...nel.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Waiman Long <Waiman.Long@...com>,
Jeff Layton <jlayton@...hat.com>,
Miklos Szeredi <mszeredi@...e.cz>,
Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Andi Kleen <andi@...stfloor.org>,
"Chandramouleeswaran, Aswin" <aswin@...com>,
"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH v7 1/4] spinlock: A new lockref structure for lockless
update of refcount
Linus Torvalds wrote:
> On Sun, Sep 8, 2013 at 5:03 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>>
>> There's one exception - basically, we decide to put duplicates of
>> reference(s) we hold into (a bunch of) structures being created. If
>> we decide that we'd failed and need to roll back, the structures
>> need to be taken out of whatever lists, etc. they'd been already
>> put on and references held in them - dropped. That removal gets done
>> under a spinlock. Sure, we can string those structures on some kind
>> of temp list, drop the spinlock and do dput() on everything in there,
>> but it's much more convenient to just free them as we are evicting
>> them, doing dput() as we go. Which is safe, since we are still have
>> the references used to create these buggers pinned down.
Dropping the spinlocks means more cores; unfortunately, a quad-core
seems to be the limit. Users must divide their time between reading
history and contributing to the present: some amount of persistent
data is a must on every user's machine. Pixel seems to be heading in
the wrong direction: that's what is stressing us out.
Ram
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