linux-kernel - Re: [PATCH] iommu/amd - Optimize PPR log handling

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Message-ID: <20180529145405.GN18595@8bytes.org>
Date:   Tue, 29 May 2018 16:54:05 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Gary R Hook <gary.hook@....com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/amd - Optimize PPR log handling

Hey Gary,

On Fri, May 18, 2018 at 04:51:56PM -0500, Gary R Hook wrote:
> Improve the performance of the PPR log polling function (i.e. the
> task of emptying the log) by minimizing MMIO operations and more
> efficiently processing groups of log entries. Cache the head
> pointer, as there's never a reason to read it. Ensure the head
> pointer register is updated every so often, to inform the IOMMU
> that space is available in the log.
> 
> Finally, since a single pass may leave logged events unread, use
> an outer loop to repeat until head has caught up to tail.
> 
> Signed-off-by: Gary R Hook <gary.hook@....com>

Do you have numbers for the performance improvement? How did you test
this patch?


Regards,

	Joerg