a32a4d8a81
Currently, on_each_cpu() and similar functions do not exploit the potential of concurrency: the function is first executed remotely and only then it is executed locally. Functions such as TLB flush can take considerable time, so this provides an opportunity for performance optimization. To do so, modify smp_call_function_many_cond(), to allows the callers to provide a function that should be executed (remotely/locally), and run them concurrently. Keep other smp_call_function_many() semantic as it is today for backward compatibility: the called function is not executed in this case locally. smp_call_function_many_cond() does not use the optimized version for a single remote target that smp_call_function_single() implements. For synchronous function call, smp_call_function_single() keeps a call_single_data (which is used for synchronization) on the stack. Interestingly, it seems that not using this optimization provides greater performance improvements (greater speedup with a single remote target than with multiple ones). Presumably, holding data structures that are intended for synchronization on the stack can introduce overheads due to TLB misses and false-sharing when the stack is used for other purposes. Signed-off-by: Nadav Amit <namit@vmware.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Link: https://lore.kernel.org/r/20210220231712.2475218-2-namit@vmware.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.