From: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
To: Nate Watterson <nwatters-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v2] iommu/arm-smmu-v3: limit use of 2-level stream tables
Date: Thu, 14 Jul 2016 14:31:07 +0100 [thread overview]
Message-ID: <20160714133107.GK29455@arm.com> (raw)
In-Reply-To: <1468347560-29924-1-git-send-email-nwatters-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
On Tue, Jul 12, 2016 at 02:19:20PM -0400, Nate Watterson wrote:
> In the current arm-smmu-v3 driver, all smmus that support 2-level
> stream tables are being forced to use them. This is suboptimal for
> smmus that support fewer stream id bits than would fill in a single
> second level table. This patch limits the use of 2-level tables to
> smmus that both support the feature and whose first level table can
> possibly contain more than a single entry.
Just to be clear, what exactly are you seeing as being suboptimal here?
Is it the memory wastage from overallocating the L2 table, or something
more?
if it's just the memory allocation, I'd sooner restrict the span field
in the L1 desc.
Will
WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] iommu/arm-smmu-v3: limit use of 2-level stream tables
Date: Thu, 14 Jul 2016 14:31:07 +0100 [thread overview]
Message-ID: <20160714133107.GK29455@arm.com> (raw)
In-Reply-To: <1468347560-29924-1-git-send-email-nwatters@codeaurora.org>
On Tue, Jul 12, 2016 at 02:19:20PM -0400, Nate Watterson wrote:
> In the current arm-smmu-v3 driver, all smmus that support 2-level
> stream tables are being forced to use them. This is suboptimal for
> smmus that support fewer stream id bits than would fill in a single
> second level table. This patch limits the use of 2-level tables to
> smmus that both support the feature and whose first level table can
> possibly contain more than a single entry.
Just to be clear, what exactly are you seeing as being suboptimal here?
Is it the memory wastage from overallocating the L2 table, or something
more?
if it's just the memory allocation, I'd sooner restrict the span field
in the L1 desc.
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: Nate Watterson <nwatters@codeaurora.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel@lists.infradead.org,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] iommu/arm-smmu-v3: limit use of 2-level stream tables
Date: Thu, 14 Jul 2016 14:31:07 +0100 [thread overview]
Message-ID: <20160714133107.GK29455@arm.com> (raw)
In-Reply-To: <1468347560-29924-1-git-send-email-nwatters@codeaurora.org>
On Tue, Jul 12, 2016 at 02:19:20PM -0400, Nate Watterson wrote:
> In the current arm-smmu-v3 driver, all smmus that support 2-level
> stream tables are being forced to use them. This is suboptimal for
> smmus that support fewer stream id bits than would fill in a single
> second level table. This patch limits the use of 2-level tables to
> smmus that both support the feature and whose first level table can
> possibly contain more than a single entry.
Just to be clear, what exactly are you seeing as being suboptimal here?
Is it the memory wastage from overallocating the L2 table, or something
more?
if it's just the memory allocation, I'd sooner restrict the span field
in the L1 desc.
Will
next prev parent reply other threads:[~2016-07-14 13:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-11 18:00 [PATCH] iommu/arm-smmu-v3: limit use of 2-level stream tables Nate Watterson
2016-07-11 18:00 ` Nate Watterson
[not found] ` <1468260059-10759-1-git-send-email-nwatters-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2016-07-12 9:36 ` Robin Murphy
2016-07-12 9:36 ` Robin Murphy
2016-07-12 9:36 ` Robin Murphy
2016-07-12 18:19 ` [PATCH v2] " Nate Watterson
2016-07-12 18:19 ` Nate Watterson
2016-07-12 18:19 ` Nate Watterson
[not found] ` <1468347560-29924-1-git-send-email-nwatters-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2016-07-14 13:31 ` Will Deacon [this message]
2016-07-14 13:31 ` Will Deacon
2016-07-14 13:31 ` Will Deacon
[not found] ` <20160714133107.GK29455-5wv7dgnIgG8@public.gmane.org>
2016-07-14 17:33 ` nwatters-sgV2jX0FEOL9JmXXK+q4OQ
2016-07-14 17:33 ` nwatters
2016-07-14 17:33 ` nwatters at codeaurora.org
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