From: Miles Chen <miles.chen@mediatek.com>
To: <robin.murphy@arm.com>
Cc: <iommu@lists.linux-foundation.org>, <joro@8bytes.org>,
<linux-kernel@vger.kernel.org>, <miles.chen@mediatek.com>,
<will@kernel.org>, <wsd_upstream@mediatek.com>,
<yf.wang@mediatek.com>, <stable@vger.kernel.org>
Subject: Re: [PATCH] iommu/iova: Improve 32-bit free space estimate
Date: Fri, 4 Mar 2022 07:36:46 +0800 [thread overview]
Message-ID: <20220303233646.13773-1-miles.chen@mediatek.com> (raw)
In-Reply-To: <033815732d83ca73b13c11485ac39336f15c3b40.1646318408.git.robin.murphy@arm.com>
Hi Robin,
> For various reasons based on the allocator behaviour and typical
> use-cases at the time, when the max32_alloc_size optimisation was
> introduced it seemed reasonable to couple the reset of the tracked
> size to the update of cached32_node upon freeing a relevant IOVA.
> However, since subsequent optimisations focused on helping genuine
> 32-bit devices make best use of even more limited address spaces, it
> is now a lot more likely for cached32_node to be anywhere in a "full"
> 32-bit address space, and as such more likely for space to become
> available from IOVAs below that node being freed.
>
> At this point, the short-cut in __cached_rbnode_delete_update() really
> doesn't hold up any more, and we need to fix the logic to reliably
> provide the expected behaviour. We still want cached32_node to only move
> upwards, but we should reset the allocation size if *any* 32-bit space
> has become available.
>
> Reported-by: Yunfei Wang <yf.wang@mediatek.com>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Would you mind adding:
Cc: <stable@vger.kernel.org>
to this path? I checked and I think the patch can be applied to
5.4 and later.
thanks,
Miles
next parent reply other threads:[~2022-03-03 23:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <033815732d83ca73b13c11485ac39336f15c3b40.1646318408.git.robin.murphy@arm.com>
2022-03-03 23:36 ` Miles Chen [this message]
2022-03-04 9:41 ` [PATCH] iommu/iova: Improve 32-bit free space estimate Joerg Roedel
2022-03-04 11:32 ` Robin Murphy
2022-03-05 0:03 ` Miles Chen
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