cb40273085
Trace a magic number as immediate value if the target variable is not found at some probe points which is based on one probe event. This feature is good for the case if you trace a source code line with some local variables, which is compiled into several instructions and some of the variables are optimized out on some instructions. Even if so, with this feature, perf probe trace a magic number instead of such disappeared variables and fold those probes on one event. E.g. without this patch: # perf probe -D "pud_page_vaddr pud" Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. Failed to find 'pud' in this function. p:probe/pud_page_vaddr _text+23480787 pud=%ax:x64 p:probe/pud_page_vaddr _text+23808453 pud=%bp:x64 p:probe/pud_page_vaddr _text+23558082 pud=%ax:x64 p:probe/pud_page_vaddr _text+328373 pud=%r8:x64 p:probe/pud_page_vaddr _text+348448 pud=%bx:x64 p:probe/pud_page_vaddr _text+23816818 pud=%bx:x64 With this patch: # perf probe -D "pud_page_vaddr pud" | head spurious_kernel_fault is blacklisted function, skip it. vmalloc_fault is blacklisted function, skip it. p:probe/pud_page_vaddr _text+23480787 pud=%ax:x64 p:probe/pud_page_vaddr _text+149051 pud=\deade12d:x64 p:probe/pud_page_vaddr _text+23808453 pud=%bp:x64 p:probe/pud_page_vaddr _text+315926 pud=\deade12d:x64 p:probe/pud_page_vaddr _text+23807209 pud=\deade12d:x64 p:probe/pud_page_vaddr _text+23557365 pud=%ax:x64 p:probe/pud_page_vaddr _text+314097 pud=%di:x64 p:probe/pud_page_vaddr _text+314015 pud=\deade12d:x64 p:probe/pud_page_vaddr _text+313893 pud=\deade12d:x64 p:probe/pud_page_vaddr _text+324083 pud=\deade12d:x64 Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org> Cc: Tom Zanussi <tom.zanussi@linux.intel.com> Link: http://lore.kernel.org/lkml/157406476931.24476.6261475888681844285.stgit@devnote2 Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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.