This change is for performance optimization.
Fixed the performance schema instrumentation interface as follows:
- simplified mysql_unlock_mutex()
- simplified mysql_unlock_rwlock()
- simplified mysql_cond_signal()
- simplified mysql_cond_broadcast()
Changed the get_thread_XXX_locker apis to have one extra parameter,
to provide memory to the instrumentation implementation.
This API change allows to use memory provided by the caller,
to avoid having to use thread local storage.
Using this extra parameter will be done in a separate fix,
this change is for the interface only.
Adjusted all the code and unit tests accordingly.
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.
client/mysqldump.c:
Pass my_free directly as its signature is compatible with the
callback type -- which wasn't the case for free_table_ent.
Fix various mismatches between function's language linkage. Any
particular function that is declared in C++ but should be callable
from C must have C linkage. Note that function types with different
linkages are also distinct. Thus, if a function type is declared in
C code, it will have C linkage (same if declared in a extern "C"
block).
client/mysql.cc:
Mismatch between prototype and declaration.
client/mysqltest.cc:
mysqltest used to be C code. Use C linkage where appropriate.
cmd-line-utils/readline/input.c:
Isolate unreachable code.
include/my_alloc.h:
Function type must have C linkage.
include/my_base.h:
Function type must have C linkage.
include/my_global.h:
Add helper macros to avoid spurious namespace indentation.
include/mysql.h.pp:
Update ABI file.
mysys/my_gethwaddr.c:
Remove stray carriage return and fix coding style.
plugin/semisync/semisync_master_plugin.cc:
Callback function types have C linkage.
plugin/semisync/semisync_slave_plugin.cc:
Callback function types have C linkage.
sql/derror.cc:
Expected function type has C linkage.
sql/field.cc:
Use helper macro and fix indentation.
sql/handler.cc:
Expected function type has C linkage.
sql/item_sum.cc:
Correct function linkages. Remove now unnecessary cast.
sql/item_sum.h:
Add prototypes with the appropriate linkage as otherwise they
are distinct.
sql/mysqld.cc:
Wrap functions in C linkage mode.
sql/opt_range.cc:
C language linkage is ignored for class member functions.
sql/partition_info.cc:
Add wrapper functions with C linkage for class member functions.
sql/rpl_utility.h:
Use helper macro and fix indentation.
sql/sql_class.cc:
Change type of thd argument -- THD is a class.
Use helper macro and fix indentation.
sql/sql_class.h:
Change type of thd argument -- THD is a class.
sql/sql_select.cc:
Expected function type has C linkage.
sql/sql_select.h:
Move prototype to sql_test.h
sql/sql_show.cc:
Expected function type has C linkage.
sql/sql_test.cc:
Fix required function prototype and fix coding style.
sql/sql_test.h:
Removed unnecessary export and add another.
storage/myisammrg/ha_myisammrg.cc:
Expected function type has C linkage.
storage/perfschema/pfs.cc:
PSI headers are declared with C language linkage, which also
applies to function types.
