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When devices with different DMA masks are using the same domain, or for PCI devices where we usually try a speculative 32-bit allocation first, there is a fair possibility that the top PFN of the rcache stack at any given time may be unsuitable for the lower limit, prompting a fallback to allocating anew from the rbtree. Consequently, we may end up artifically increasing pressure on the 32-bit IOVA space as unused IOVAs accumulate lower down in the rcache stacks, while callers with 32-bit masks also impose unnecessary rbtree overhead. In such cases, let's try a bit harder to satisfy the allocation locally first - scanning the whole stack should still be relatively inexpensive. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.