From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH v2] iommu/iova: Try harder to allocate from rcache magazine Date: Thu, 28 Sep 2017 15:41:16 +0200 Message-ID: <20170928134115.GS8398@8bytes.org> References: <8127fabc219811d8169189e9d7177d42bc74bcbf.1505827369.git.robin.murphy@arm.com> <8e319924684be401103a5831acee6895d7c5b6d6.1506594488.git.robin.murphy@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <8e319924684be401103a5831acee6895d7c5b6d6.1506594488.git.robin.murphy@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: Robin Murphy Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org List-Id: iommu@lists.linux-foundation.org On Thu, Sep 28, 2017 at 11:31:23AM +0100, Robin Murphy wrote: > When devices with different DMA masks are using the same domain, or for > PCI devices where we usually try a speculative 32-bit allocation first, > there is a fair possibility that the top PFN of the rcache stack at any > given time may be unsuitable for the lower limit, prompting a fallback > to allocating anew from the rbtree. Consequently, we may end up > artifically increasing pressure on the 32-bit IOVA space as unused IOVAs > accumulate lower down in the rcache stacks, while callers with 32-bit > masks also impose unnecessary rbtree overhead. > > In such cases, let's try a bit harder to satisfy the allocation locally > first - scanning the whole stack should still be relatively inexpensive. > > Signed-off-by: Robin Murphy > --- > > v2: There's no need for a 'proper' stack rotation > > drivers/iommu/iova.c | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) Thanks, applied the series.