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set/show code-cache

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Similar to stack cache, in this patch, we add
TARGET_OBJECT_CODE_MEMORY to read code from target and add a new
option "set code-cache on|off" to optimize code accesses by
using the target memory cache.

In V4:
 - Remove "without affecting correctness" from NEWS and doc.
 - Replace "ON" with "on" in doc.
 - "access" -> "accesses".

In V3:
 - Rename functions and variables.
 - Update command help, doc and NEWS entry.
 - Invalidate cache on option transitions, to align with
   the behaviour of "stack-cache".  Since cache invalidation is
   transparent to users, users don't know option "stack-cache"
   transitions cause code cache invalidation.

V2 was reviewed by Doug.  There are some changes in V3, so I post it
here.

gdb:

2013-11-24  Yao Qi  <yao@codesourcery.com>

	* NEWS: Add note on new "set code-cache" option.
	* target-dcache.c (code_cache_enabled_1): New variable.
	(code_cache_enabled): New variable.
	(show_code_cache, set_code_cache): New function.
	(code_cache_enabled_p): New function.
	(_initialize_target_dcache): Register command.
	* target-dcache.h (code_cache_enabled_p): Declare.
	* target.c (memory_xfer_partial_1):Handle
	TARGET_OBJECT_CODE_MEMORY and code_cache_enabled.
	(target_read_code): New function.
	* target.h (enum target_object) <TARGET_OBJECT_CODE_MEMORY>:
	New.
	(target_read_code): Declare.

gdb/doc:

2013-11-24  Yao Qi  <yao@codesourcery.com>

	* gdb.texinfo (Caching Remote Data): Document new
	"set/show stack-cache" option.
This commit is contained in:
Yao Qi 2013-11-01 12:26:10 +08:00
parent 0fb14d8ffd
commit 29453a1455
8 changed files with 118 additions and 5 deletions
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16
gdb/ChangeLog
View File

@ -1,3 +1,19 @@
2013-11-24 Yao Qi <yao@codesourcery.com>
* NEWS: Add note on new "set code-cache" option.
* target-dcache.c (code_cache_enabled_1): New variable.
(code_cache_enabled): New variable.
(show_code_cache, set_code_cache): New function.
(code_cache_enabled_p): New function.
(_initialize_target_dcache): Register command.
* target-dcache.h (code_cache_enabled_p): Declare.
* target.c (memory_xfer_partial_1):Handle
TARGET_OBJECT_CODE_MEMORY and code_cache_enabled.
(target_read_code): New function.
* target.h (enum target_object) <TARGET_OBJECT_CODE_MEMORY>:
New.
(target_read_code): Declare.
2013-11-24 Yao Qi <yao@codesourcery.com>
* target-dcache.c (stack_cache_enabled_p_1): Rename to ...

5
gdb/NEWS
View File

@ -117,6 +117,11 @@ show startup-with-shell
Specifies whether Unix child processes are started via a shell or
directly.
set code-cache
show code-cache
Use the target memory cache for accesses to the code segment. This
improves performance of remote debugging (particularly disassembly).
* You can now use a literal value 'unlimited' for options that
interpret 0 or -1 as meaning "unlimited". E.g., "set
trace-buffer-size unlimited" is now an alias for "set

5
gdb/doc/ChangeLog
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@ -1,3 +1,8 @@
2013-11-24 Yao Qi <yao@codesourcery.com>
* gdb.texinfo (Caching Remote Data): Document new
"set/show stack-cache" option.
2013-11-24 Yao Qi <yao@codesourcery.com>
* gdb.texinfo (Caching Target Data): Replace "ON" with "on".

15
gdb/doc/gdb.texinfo
View File

@ -10842,7 +10842,8 @@ Therefore, by default, @value{GDBN} only caches data
known to be on the stack@footnote{In non-stop mode, it is moderately
rare for a running thread to modify the stack of a stopped thread
in a way that would interfere with a backtrace, and caching of
stack reads provides a significant speed up of remote backtraces.}.
stack reads provides a significant speed up of remote backtraces.} or
in the code segment.
Other regions of memory can be explicitly marked as
cacheable; @pxref{Memory Region Attributes}.
@ -10867,6 +10868,18 @@ caching. By default, this option is @code{on}.
@item show stack-cache
Show the current state of data caching for memory accesses.
@kindex set code-cache
@item set code-cache on
@itemx set code-cache off
Enable or disable caching of code segment accesses. When @code{on},
use caching. By default, this option is @code{on}. This improves
performance of disassembly in remote debugging.
@kindex show code-cache
@item show code-cache
Show the current state of target memory cache for code segment
accesses.
@kindex info dcache
@item info dcache @r{[}line@r{]}
Print the information about the performance of data cache of the

52
gdb/target-dcache.c
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@ -124,6 +124,46 @@ stack_cache_enabled_p (void)
return stack_cache_enabled;
}
/* The option sets this. */
static int code_cache_enabled_1 = 1;
/* And set_code_cache updates this.
The reason for the separation is so that we don't flush the cache for
on->on transitions. */
static int code_cache_enabled = 1;
/* This is called *after* the code-cache has been set.
Flush the cache for off->on and on->off transitions.
There's no real need to flush the cache for on->off transitions,
except cleanliness. */
static void
set_code_cache (char *args, int from_tty, struct cmd_list_element *c)
{
if (code_cache_enabled != code_cache_enabled_1)
target_dcache_invalidate ();
code_cache_enabled = code_cache_enabled_1;
}
/* Show option "code-cache". */
static void
show_code_cache (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
fprintf_filtered (file, _("Cache use for code accesses is %s.\n"), value);
}
/* Return true if "code cache" is enabled, otherwise, return false. */
int
code_cache_enabled_p (void)
{
return code_cache_enabled;
}
/* -Wmissing-prototypes */
extern initialize_file_ftype _initialize_target_dcache;
@ -141,6 +181,18 @@ By default, caching for stack access is on."),
show_stack_cache,
&setlist, &showlist);
add_setshow_boolean_cmd ("code-cache", class_support,
&code_cache_enabled_1, _("\
Set cache use for code segment access."), _("\
Show cache use for code segment access."), _("\
When on, use the target memory cache for all code segment accesses,\n\
regardless of any configured memory regions. This improves remote\n\
performance significantly. By default, caching for code segment\n\
access is on."),
set_code_cache,
show_code_cache,
&setlist, &showlist);
target_dcache_aspace_key
= register_address_space_data_with_cleanup (NULL,
target_dcache_cleanup);

2
gdb/target-dcache.h
View File

@ -30,4 +30,6 @@ extern int target_dcache_init_p (void);
extern int stack_cache_enabled_p (void);
extern int code_cache_enabled_p (void);
#endif /* TARGET_DCACHE_H */

23
gdb/target.c
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@ -1547,7 +1547,8 @@ memory_xfer_partial_1 (struct target_ops *ops, enum target_object object,
the collected memory range fails. */
&& get_traceframe_number () == -1
&& (region->attrib.cache
|| (stack_cache_enabled_p () && object == TARGET_OBJECT_STACK_MEMORY)))
|| (stack_cache_enabled_p () && object == TARGET_OBJECT_STACK_MEMORY)
|| (code_cache_enabled_p () && object == TARGET_OBJECT_CODE_MEMORY)))
{
DCACHE *dcache = target_dcache_get_or_init ();
@ -1600,8 +1601,8 @@ memory_xfer_partial_1 (struct target_ops *ops, enum target_object object,
&& writebuf != NULL
&& target_dcache_init_p ()
&& !region->attrib.cache
&& stack_cache_enabled_p ()
&& object != TARGET_OBJECT_STACK_MEMORY)
&& ((stack_cache_enabled_p () && object != TARGET_OBJECT_STACK_MEMORY)
|| (code_cache_enabled_p () && object != TARGET_OBJECT_CODE_MEMORY)))
{
DCACHE *dcache = target_dcache_get ();
@ -1697,7 +1698,8 @@ target_xfer_partial (struct target_ops *ops,
/* If this is a memory transfer, let the memory-specific code
have a look at it instead. Memory transfers are more
complicated. */
if (object == TARGET_OBJECT_MEMORY || object == TARGET_OBJECT_STACK_MEMORY)
if (object == TARGET_OBJECT_MEMORY || object == TARGET_OBJECT_STACK_MEMORY
|| object == TARGET_OBJECT_CODE_MEMORY)
retval = memory_xfer_partial (ops, object, readbuf,
writebuf, offset, len);
else
@ -1799,6 +1801,19 @@ target_read_stack (CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len)
return TARGET_XFER_E_IO;
}
/* Like target_read_memory, but specify explicitly that this is a read from
the target's code. This may trigger different cache behavior. */
int
target_read_code (CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len)
{
if (target_read (current_target.beneath, TARGET_OBJECT_CODE_MEMORY, NULL,
myaddr, memaddr, len) == len)
return 0;
else
return TARGET_XFER_E_IO;
}
/* Write LEN bytes from MYADDR to target memory at address MEMADDR.
Returns either 0 for success or a target_xfer_error value if any
error occurs. If an error occurs, no guarantee is made about how

5
gdb/target.h
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@ -145,6 +145,9 @@ enum target_object
if it is not in a region marked as such, since it is known to be
"normal" RAM. */
TARGET_OBJECT_STACK_MEMORY,
/* Memory known to be part of the target code. This is cached even
if it is not in a region marked as such. */
TARGET_OBJECT_CODE_MEMORY,
/* Kernel Unwind Table. See "ia64-tdep.c". */
TARGET_OBJECT_UNWIND_TABLE,
/* Transfer auxilliary vector. */
@ -1050,6 +1053,8 @@ extern int target_read_memory (CORE_ADDR memaddr, gdb_byte *myaddr,
extern int target_read_stack (CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len);
extern int target_read_code (CORE_ADDR memaddr, gdb_byte *myaddr, ssize_t len);
extern int target_write_memory (CORE_ADDR memaddr, const gdb_byte *myaddr,
ssize_t len);