From: John Garry <john.garry@huawei.com>
To: Robin Murphy <robin.murphy@arm.com>,
"Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>,
Will Deacon <will@kernel.org>, Joerg Roedel <joro@8bytes.org>,
iommu <iommu@lists.linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>, Linuxarm <linuxarm@huawei.com>
Subject: Re: [PATCH 1/1] Revert "iommu/iova: Retry from last rb tree node if iova search fails"
Date: Tue, 2 Mar 2021 12:30:51 +0000 [thread overview]
Message-ID: <0cb64d74-0ec1-2284-f67a-b1619a3eb138@huawei.com> (raw)
In-Reply-To: <d090b869-b3ac-fecc-9efd-d870e43e0d99@huawei.com>
On 01/03/2021 15:48, John Garry wrote:
>>
>> While max32_alloc_size indirectly tracks the largest*contiguous*
>> available space, one of the ideas from which it grew was to simply keep
>> count of the total number of free PFNs. If you're really spending
>> significant time determining that the tree is full, as opposed to just
>> taking longer to eventually succeed, then it might be relatively
>> innocuous to tack on that semi-redundant extra accounting as a
>> self-contained quick fix for that worst case.
>>
>>> Anyway, we see ~50% throughput regression, which is intolerable. As seen
>>> in [0], I put this down to the fact that we have so many IOVA requests
>>> which exceed the rcache size limit, which means many RB tree accesses
>>> for non-cacheble IOVAs, which are now slower.
>
> I will attempt to prove this by increasing RCACHE RANGE, such that all
> IOVA sizes may be cached.
About this one, as expected, we restore performance by increasing the
RCACHE RANGE.
Some figures:
Baseline v5.12-rc1
strict mode:
600K IOPs
Revert "iommu/iova: Retry from last rb tree node if iova search fails":
1215K
Increase IOVA RCACHE range 6 -> 10 (All IOVAs size requests now
cacheable for this experiment):
1400K
Reduce LLDD max SGE count 124 -> 16:
1288K
non-strict mode
1650K
So ideally we can work towards something for which IOVAs of all size
could be cached.
Cheers,
John
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next prev parent reply other threads:[~2021-03-02 12:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-29 9:21 [PATCH 1/1] Revert "iommu/iova: Retry from last rb tree node if iova search fails" Zhen Lei
2021-01-29 9:48 ` Leizhen (ThunderTown)
2021-01-29 12:03 ` Robin Murphy
2021-01-29 12:43 ` chenxiang (M)
2021-02-25 13:54 ` John Garry
2021-03-01 13:20 ` Robin Murphy
2021-03-01 15:48 ` John Garry
2021-03-02 12:30 ` John Garry [this message]
2021-03-08 15:15 ` Robin Murphy
2021-03-08 16:22 ` John Garry
2021-03-10 17:50 ` John Garry
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