linux-kernel - Re: [PATCH v4] vfio/type1: optimize vfio_pin_pages

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Message-ID: <810975b2-7a6f-4c81-a827-40a6765b7d3e@redhat.com>
Date: Wed, 21 May 2025 08:36:40 +0200
From: David Hildenbrand <david@...hat.com>
To: lizhe.67@...edance.com, alex.williamson@...hat.com
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, muchun.song@...ux.dev,
 peterx@...hat.com
Subject: Re: [PATCH v4] vfio/type1: optimize vfio_pin_pages_remote() for large
 folios

On 21.05.25 06:25, lizhe.67@...edance.com wrote:
> From: Li Zhe <lizhe.67@...edance.com>
> 
> When vfio_pin_pages_remote() is called with a range of addresses that
> includes large folios, the function currently performs individual
> statistics counting operations for each page. This can lead to significant
> performance overheads, especially when dealing with large ranges of pages.
> 
> This patch optimize this process by batching the statistics counting
> operations.
> 
> The performance test results for completing the 8G VFIO IOMMU DMA mapping,
> obtained through trace-cmd, are as follows. In this case, the 8G virtual
> address space has been mapped to physical memory using hugetlbfs with
> pagesize=2M.
> 
> Before this patch:
> funcgraph_entry:      # 33813.703 us |  vfio_pin_map_dma();
> 
> After this patch:
> funcgraph_entry:      # 16071.378 us |  vfio_pin_map_dma();
> 
> Signed-off-by: Li Zhe <lizhe.67@...edance.com>
> Co-developed-by: Alex Williamson <alex.williamson@...hat.com>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
> Changelogs:
> 
> v3->v4:
> - Use min_t() to obtain the step size, rather than min().
> - Fix some issues in commit message and title.

It's usually a good idea to wait with re submissions until the 
discussions on the previous version have ended.

-- 
Cheers,

David / dhildenb