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aaebf69062
the blkfront driver to perform I/Os of up to 2 MB, subject to support from the blkback to which it is connected and the initiation of such large I/Os by the rest of the kernel. In practice, the I/O size is increased from 40 kB to 128 kB. The changes to xen/interface/io/blkif.h consist merely of merging updates from the upstream Xen repository. In dev/xen/blkfront/block.h we add some convenience macros and structure fields used for indirect-page I/Os: The device records its negotiated limit on the number of indirect pages used, while each I/O command structure gains permanently allocated page(s) for indirect page references and the Xen grant references for those pages. In dev/xen/blkfront/blkfront.c we now check in xbd_queue_cb whether a request is small enough to handle without an indirection page, and either follow the previous behaviour or use new code for issuing an indirect segment I/O. In xbd_connect we read the size of indirect segment I/Os supported by the backend and select the maximum size we will use; then allocate the pages and Xen grant references for each I/O command structure. In xbd_free those grants and pages are released. A new loader tunable, hw.xbd.xbd_enable_indirect, can be set to 0 in order to disable this functionality; it works by pretending that the backend does not support this feature. Some backends exhibit a loss of performance with large I/Os, so users may wish to test with and without this functionality enabled. Reviewed by: royger MFC after: 3 days Relnotes: yes |
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| .. | ||
| arch-arm/hvm | ||
| arch-x86 | ||
| foreign | ||
| hvm | ||
| io | ||
| xsm | ||
| acm.h | ||
| acm_ops.h | ||
| arch-arm.h | ||
| arch-powerpc.h | ||
| arch-x86_32.h | ||
| arch-x86_64.h | ||
| callback.h | ||
| COPYING | ||
| dom0_ops.h | ||
| domctl.h | ||
| elfnote.h | ||
| elfstructs.h | ||
| event_channel.h | ||
| features.h | ||
| grant_table.h | ||
| kexec.h | ||
| libelf.h | ||
| mem_event.h | ||
| memory.h | ||
| nmi.h | ||
| physdev.h | ||
| platform.h | ||
| sched.h | ||
| sysctl.h | ||
| tmem.h | ||
| trace.h | ||
| vcpu.h | ||
| version.h | ||
| xen-compat.h | ||
| xen.h | ||
| xencomm.h | ||
| xenoprof.h | ||