linux-kernel - Re: [PATCH v2 10/10] mm, cma: use spinlock instead of mutex

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Date:	Thu, 12 Jun 2014 16:56:38 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Gleb Natapov <gleb@...nel.org>, Alexander Graf <agraf@...e.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kvm@...r.kernel.org, kvm-ppc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 10/10] mm, cma: use spinlock instead of mutex

On Thu, Jun 12, 2014 at 04:40:29PM +0900, Minchan Kim wrote:
> On Thu, Jun 12, 2014 at 12:21:47PM +0900, Joonsoo Kim wrote:
> > Currently, we should take the mutex for manipulating bitmap.
> > This job may be really simple and short so we don't need to sleep
> > if contended. So I change it to spinlock.
> 
> I'm not sure it would be good always.
> Maybe you remember we discussed about similar stuff about bitmap
> searching in vmap friend internally, which was really painful
> when it was fragmented. So, at least we need number if you really want
> and I hope the number from ARM machine most popular platform for CMA
> at the moment.

Good Point!! Agreed. I will drop this one in next spin and re-submit
in separate patchset after some testing.

Thanks.
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