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9f5b681e2a
Flush queues currently use a fixed compile time size of 256 entries. This being a power of 2 allows the compiler to use shift and mask instead of more expensive modulo operations. With per-CPU flush queues larger queue sizes would hit per-CPU allocation limits, with a single flush queue these limits do not apply however. Also with single queues being particularly suitable for virtualized environments with expensive IOTLB flushes these benefit especially from larger queues and thus fewer flushes. To this end re-order struct iova_fq so we can use a dynamic array and introduce the flush queue size and timeouts as new options in the iommu_dma_options struct. So as not to lose the shift and mask optimization, use a power of 2 for the length and use explicit shift and mask instead of letting the compiler optimize this. A large queue size and 1 second timeout is then set for the shadow on flush case set by s390 paged memory guests. This then brings performance on par with the previous s390 specific DMA API implementation. Acked-by: Robin Murphy <robin.murphy@arm.com> Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com> #s390 Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Link: https://lore.kernel.org/r/20230928-dma_iommu-v13-6-9e5fc4dacc36@linux.ibm.com Signed-off-by: Joerg Roedel <jroedel@suse.de> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.