linux-kernel - Re: [PATCH v3 2/2] iommu: Remove cpu-local spinlock

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Message-ID: <20160615122223.GI26566@8bytes.org>
Date:	Wed, 15 Jun 2016 14:22:23 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	intel-gfx@...ts.freedesktop.org,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] iommu: Remove cpu-local spinlock

On Wed, Jun 01, 2016 at 12:10:09PM +0100, Chris Wilson wrote:
> By avoiding cross-CPU usage of the per-cpu iova cache, we can forgo
> having a spinlock inside the per-cpu struct. The only place where we
> actually may touch another CPU's data is when performing a cache flush
> after running out of memory. Here, we can instead schedule a task to run
> on the other CPU to do the flush before trying again.

The big benefit of the spinlock is that the rcache can be flushed from a
different cpu without the need to send IPIs to everyone.


	Joerg