df323337e5
The get_buffers() macro may provide one or two buffers to the caller. Those buffers are pre-allocated on init for each CPU. By default it allocates 2* 2 * MAX_PATH * POSSIBLE_CPU which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so on. Replace the per-CPU buffers with a common memory pool which is shared across all CPUs. The pool grows on demand and never shrinks. The pool starts with two (UP) or four (SMP) elements. By using this pool it is possible to request a buffer and keeping preemption enabled which avoids the hack in profile_transition(). It has been pointed out by Tetsuo Handa that GFP_KERNEL allocations for small amount of memory do not fail. In order not to have an endless retry, __GFP_RETRY_MAYFAIL is passed (so the memory allocation is not repeated until success) and retried once hoping that in the meantime a buffer has been returned to the pool. Since now NULL is possible all allocation paths check the buffer pointer and return -ENOMEM on failure. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: John Johansen <john.johansen@canonical.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.