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A bus lock can be thousands of cycles slower than atomic operation within one cache line. It also disrupts performance on other cores. Malicious users can generate multiple bus locks to degrade the whole system performance. The current mitigation is to kill the offending process, but for certain scenarios it's desired to identify and throttle the offending application. Add a system wide rate limit for bus locks. When the system detects bus locks at a rate higher than N/sec (where N can be set by the kernel boot argument in the range [1..1000]) any task triggering a bus lock will be forced to sleep for at least 20ms until the overall system rate of bus locks drops below the threshold. Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Tony Luck <tony.luck@intel.com> Link: https://lore.kernel.org/r/20210419214958.4035512-3-fenghua.yu@intel.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.