Waiman Long af161bee93 include/linux/sched/mm.h: optimize current_gfp_context()
The current_gfp_context() converts a number of PF_MEMALLOC_* per-process
flags into the corresponding GFP_* flags for memory allocation.  In that
function, current->flags is accessed 3 times.  That may lead to duplicated
access of the same memory location.

This is not usually a problem with minimal debug config options on as the
compiler can optimize away the duplicated memory accesses.  With most of
the debug config options on, however, that may not be the case.  For
example, the x86-64 object size of the __need_fs_reclaim() in a debug
kernel that calls current_gfp_context() was 309 bytes.  With this patch
applied, the object size is reduced to 202 bytes.  This is a saving of 107
bytes and will probably be slightly faster too.

Use READ_ONCE() to access current->flags to prevent the compiler from
possibly accessing current->flags multiple times.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michel Lespinasse <walken@google.com>
Link: http://lkml.kernel.org/r/20200618212936.9776-1-longman@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-12 10:57:57 -07:00
2020-08-10 19:07:44 -07:00
2020-08-10 19:07:44 -07:00
2020-08-10 19:07:44 -07:00
2020-08-09 14:10:26 -07:00
2020-08-10 19:07:44 -07:00
2020-08-09 14:10:26 -07:00
2020-08-09 14:10:26 -07:00
2020-08-06 14:27:31 -07:00
2020-08-10 19:07:44 -07:00
2020-08-07 18:48:15 -07:00
2020-08-09 14:10:26 -07:00

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.
Description
Linux kernel source tree
Readme 3.3 GiB
Languages
C 97.5%
Assembly 1%
Shell 0.6%
Python 0.3%
Makefile 0.3%