linux-kernel - Re: [PATCH v2] iommu/iova: Optimize alloc_iova with rbtree

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Message-ID: <4527c925-076b-a477-4ff8-697d75f16761@bytedance.com>
Date:   Fri, 26 Aug 2022 18:28:39 +0800
From:   Peng Zhang <zhangpeng.00@...edance.com>
To:     Ethan Zhao <haifeng.zhao@...ux.intel.com>, joro@...tes.org,
        will@...nel.org
Cc:     iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        robin.murphy@....com
Subject: Re: [PATCH v2] iommu/iova: Optimize alloc_iova with rbtree_augmented


> Though only 3-4 drivers use alloc_iova() directly, in my understanding
> 
> your test has simulated the worst case, rcache doesn't work at all,
> 
> "alloc_iova" +“remove_iova” number looks great for worst case.

There is another case, when the size to allocate greater to 2^5, even if 
alloc_iova_fast() is used, alloc_iova() will always be called because 
the maximum iova size that rcache supports to allocate is 32.
IOVA_RANGE_CACHE_MAX_SIZE specifies the maximum size.

Thanks,

Peng