Messages in this thread | | | Date | Wed, 22 Mar 2023 15:32:30 +0100 | Subject | Re: [PATCH 1/1] swiotlb: Track and report io_tlb_used high water mark in debugfs | From | Petr Tesarik <> |
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Hi,
On 2/27/2023 5:41 PM, Michael Kelley wrote: > swiotlb currently reports the total number of slabs and the instantaneous > in-use slabs in debugfs. But with increased usage of swiotlb for all I/O > in Confidential Computing (coco) VMs, it has become difficult to know > how much memory to allocate for swiotlb bounce buffers, either via the > automatic algorithm in the kernel or by specifying a value on the > kernel boot line. The current automatic algorithm generously allocates > swiotlb bounce buffer memory, and may be wasting significant memory in > many use cases.
I like the idea. Tracking and exposing the high watermark is definitely a step in the right direction. I would also appreciate an indicator of fragmentation, but that can be implemented later.
However, you apparently have a scenario where swiotlb is used intensely. Are you able to measure swiotlb performance? If yes, can you suggest a suitable method? I'm asking for my work on making swiotlb more flexible (able to grow and shrink).
Petr T
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