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Currently, if enable_pml=1 PML remains enabled for the entire lifetime of the VM irrespective of whether dirty logging is enable or disabled. When dirty logging is disabled, all the pages of the VM are manually marked dirty, so that PML is effectively non-operational. Setting the dirty bits is an expensive operation which can cause severe MMU lock contention in a performance sensitive path when dirty logging is disabled after a failed or canceled live migration. Manually setting dirty bits also fails to prevent PML activity if some code path clears dirty bits, which can incur unnecessary VM-Exits. In order to avoid this extra overhead, dynamically enable/disable PML when dirty logging gets turned on/off for the first/last memslot. Signed-off-by: Makarand Sonare <makarandsonare@google.com> Co-developed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20210213005015.1651772-12-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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.