mirror of https://gitee.com/openkylin/linux.git
9f82e90a66
Current implementation relies on L1 line length which might easily be smaller than L2 line (which is usually the case BTW). Imagine this typical case: L2 line is 128 bytes while L1 line is 64-bytes. Now we want to allocate small buffer and later use it for DMA (consider IOC is not available). kmalloc() allocates small KMALLOC_MIN_SIZE-sized, KMALLOC_MIN_SIZE-aligned That way if buffer happens to be aligned to L1 line and not L2 line we'll be flushing and invalidating extra portions of data from L2 which will cause cache coherency issues. And since KMALLOC_MIN_SIZE is bound to ARCH_DMA_MINALIGN the fix could be simple - set ARCH_DMA_MINALIGN to the largest cache line we may ever get. As of today neither L1 of ARC700 and ARC HS38 nor SLC might not be longer than 128 bytes. Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com> |
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README
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.