17bebcc68e
Introduce a minimal interface for doing counter measurements of small units of work within the kernel. Use the kernel_cpumcf_begin() function start a measurement session and, later, stop it with kernel_cpumcf_end(). During the measreument session, you can enable and start/stop counter sets by using ctr_set_* functions. To make these changes effective use the lcctl() function. You can then use the ecctr() function to extract counters from the different counter sets. Please note that you have to check whether the counter sets to be enabled are authorized. Note that when a measurement session is active, other users cannot perform counter measurements. In such cases, kernel_cpumcf_begin() indicates this with returning -EBUSY. If the counter facility is not available, kernel_cpumcf_begin() returns -ENODEV. Note that this interface is restricted to the current CPU and, thus, preemption must be turned off. Example: u32 state, err; u64 cycles, insn; err = kernel_cpumcf_begin(); if (err) goto out_busy; state = 0; ctr_set_enable(&state, CPUMF_CTR_SET_BASIC); ctr_set_start(&state, CPUMF_CTR_SET_BASIC); err = lcctl(state); if (err) goto ; /* ... do your work ... */ ctr_set_stop(&state, CPUMF_CTR_SET_BASIC); err = lcctl(state); if (err) goto out; cycles = insn = 0; ecctr(0, &cycles); ecctr(1, &insn); /* ... */ kernel_cpumcf_end(); out_busy: Signed-off-by: Hendrik Brueckner <brueckner@linux.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.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.