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23e118a48a
Currently when the pci-hyperv driver finishes probing and initializing the PCI device, it sets the PCI_COMMAND_MEMORY bit; later when the PCI device is registered to the core PCI subsystem, the core PCI driver's BAR detection and initialization code toggles the bit multiple times, and each toggling of the bit causes the hypervisor to unmap/map the virtual BARs from/to the physical BARs, which can be slow if the BAR sizes are huge, e.g., a Linux VM with 14 GPU devices has to spend more than 3 minutes on BAR detection and initialization, causing a long boot time. Reduce the boot time by not setting the PCI_COMMAND_MEMORY bit when we register the PCI device (there is no need to have it set in the first place). The bit stays off till the PCI device driver calls pci_enable_device(). With this change, the boot time of such a 14-GPU VM is reduced by almost 3 minutes. Link: https://lore.kernel.org/lkml/20220419220007.26550-1-decui@microsoft.com/ Tested-by: Boqun Feng (Microsoft) <boqun.feng@gmail.com> Signed-off-by: Dexuan Cui <decui@microsoft.com> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Cc: Jake Oshins <jakeo@microsoft.com> Link: https://lore.kernel.org/r/20220502074255.16901-1-decui@microsoft.com Signed-off-by: Wei Liu <wei.liu@kernel.org> |
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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.