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Michael Kelley authored
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. To support better understanding of swiotlb usage, add tracking of the the high water mark for usage of the default swiotlb bounce buffer memory pool and any reserved memory pools. Report these high water marks in debugfs along with the other swiotlb pool metrics. Allow the high water marks to be reset to zero at runtime by writing to them. Signed-off-by:
Michael Kelley <mikelley@microsoft.com> Signed-off-by:
Christoph Hellwig <hch@lst.de>
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