Re: [PATCH 05/10] Invalidate or shrink dcache when setting is changed.

[Yao Qi <yao at codesourcery dot com>]

On 11/18/2013 04:34 AM, Doug Evans wrote:
> It feels simpler if this were:
> 
>    if (target_dcache_init_p ())
>      dcache_check_resize (target_dcache);
>    return target_dcache;
> 
> There may be a better name than dcache_check_resize, one may want to
> call it for situations other than resizings, but here target-dcache.c
> is using 3 API routines from dcache.c to achieve what is essentially
> one operation: check if the cache needs to be reconfigured and update
> if so.

How about "dcache_update_config"?

> 
>> >@@ -54,7 +62,14 @@ target_dcache_get (void)
>> >  DCACHE *
>> >  target_dcache_get_or_init (void)
>> >  {
>> >-  if (!target_dcache_init_p ())
>> >+  if (target_dcache_init_p ())
>> >+    {
>> >+      if (dcache_invalidate_p (target_dcache))
>> >+       dcache_invalidate (target_dcache);
>> >+
>> >+      dcache_shrink (target_dcache);
>> >+    }
>> >+  else
>> >      target_dcache = dcache_init ();
>> >
>> >    return target_dcache;
> I think it would be better to remove the duplication and have:
> 
>    if (target_dcache_init_p ())
>      return target_dcache_get ();

Fixed.

-- 
Yao (éå)

gdb:

2013-11-18  Yao Qi  <yao@codesourcery.com>

	* dcache.c (dcache_evict): New function.
	(dcache_shrink): New function.
	(dcache_update_config): New function.
	(dcache_alloc): Call dcache_evict.
	(set_dcache_size): Remove call target_dcache_invalidate.
	(set_dcache_line_size): Likewise.
	* dcache.h (dcache_update_config): Declare.
	* target-dcache.c (target_dcache_get): Invalidate and shrink
	cache if necessary.
	(target_dcache_get_or_init): Likewise.

gdb/doc:

2013-11-18  Yao Qi  <yao@codesourcery.com>

	* gdb.texinfo (Caching Target Data): Update document of
	commands 'set dcache size' and 'set dcache line-size'.
---
 gdb/dcache.c        |   53 ++++++++++++++++++++++++++++++++++++++++++--------
 gdb/dcache.h        |    2 +
 gdb/doc/gdb.texinfo |    7 ++++-
 gdb/target-dcache.c |    7 +++++-
 4 files changed, 57 insertions(+), 12 deletions(-)

diff --git a/gdb/dcache.c b/gdb/dcache.c
index 5b32629..4474be4 100644
--- a/gdb/dcache.c
+++ b/gdb/dcache.c
@@ -243,6 +243,49 @@ invalidate_block (struct dcache_block *block, void *param)
   append_block (&dcache->freelist, block);
 }
 
+/* Evict the cache line decided by the eviction algorithm.  Return the
+   evicted cache line.  */
+
+static struct dcache_block *
+dcache_evict (DCACHE *dcache)
+{
+  /* Evict the least recently allocated line.  */
+  struct dcache_block *db = dcache->oldest;
+
+  remove_block (&dcache->oldest, db);
+  splay_tree_remove (dcache->tree, (splay_tree_key) db->addr);
+
+  return db;
+}
+
+/* Shrink DCACHE if it is over-sized.  */
+
+static void
+dcache_shrink (DCACHE *dcache)
+{
+  while (dcache->size > dcache_size)
+    {
+      struct dcache_block *db = dcache_evict (dcache);
+
+      free_block (db, NULL);
+      dcache->size--;
+    }
+}
+
+/* Update the configuration, such as line-size, of DCACHE if
+   necessary.  */
+
+void
+dcache_update_config (DCACHE *dcache)
+{
+  /* DCACHE must be invalidated if its line-size is different from the
+     global setting.  */
+  if (dcache->line_size != dcache_line_size)
+    dcache_invalidate (dcache);
+
+  dcache_shrink (dcache);
+}
+
 /* Free all the data cache blocks, thus discarding all cached data.  */
 
 void
@@ -359,13 +402,7 @@ dcache_alloc (DCACHE *dcache, CORE_ADDR addr)
   struct dcache_block *db;
 
   if (dcache->size >= dcache_size)
-    {
-      /* Evict the least recently allocated line.  */
-      db = dcache->oldest;
-      remove_block (&dcache->oldest, db);
-
-      splay_tree_remove (dcache->tree, (splay_tree_key) db->addr);
-    }
+    db = dcache_evict (dcache);
   else
     {
       db = dcache->freelist;
@@ -669,7 +706,6 @@ set_dcache_size (char *args, int from_tty,
       dcache_size = DCACHE_DEFAULT_SIZE;
       error (_("Dcache size must be greater than 0."));
     }
-  target_dcache_invalidate ();
 }
 
 static void
@@ -683,7 +719,6 @@ set_dcache_line_size (char *args, int from_tty,
       dcache_line_size = DCACHE_DEFAULT_LINE_SIZE;
       error (_("Invalid dcache line size: %u (must be power of 2)."), d);
     }
-  target_dcache_invalidate ();
 }
 
 static void
diff --git a/gdb/dcache.h b/gdb/dcache.h
index 720a887..d2fcd6a 100644
--- a/gdb/dcache.h
+++ b/gdb/dcache.h
@@ -40,4 +40,6 @@ int dcache_xfer_memory (struct target_ops *ops, DCACHE *cache, CORE_ADDR mem,
 void dcache_update (DCACHE *dcache, CORE_ADDR memaddr, gdb_byte *myaddr,
 		    int len);
 
+void dcache_update_config (DCACHE *dcache);
+
 #endif /* DCACHE_H */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 8377ca8..16ae0c8 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -10878,13 +10878,16 @@ printed in hex.
 @item set dcache size @var{size}
 @cindex dcache size
 @kindex set dcache size
-Set maximum number of entries in dcache (dcache depth above).
+Set maximum number of entries in dcache (dcache depth above).  When
+the dcache is being used, if its size is greater than this setting, it
+is shrunk.
 
 @item set dcache line-size @var{line-size}
 @cindex dcache line-size
 @kindex set dcache line-size
 Set number of bytes each dcache entry caches (dcache width above).
-Must be a power of 2.
+Must be a power of 2.  When the dcache is being used, if its width is
+different from this setting, it is invalidated.
 
 @item show dcache size
 @kindex show dcache size
diff --git a/gdb/target-dcache.c b/gdb/target-dcache.c
index bf04679..6bd576d 100644
--- a/gdb/target-dcache.c
+++ b/gdb/target-dcache.c
@@ -45,6 +45,9 @@ target_dcache_invalidate (void)
 DCACHE *
 target_dcache_get (void)
 {
+  if (target_dcache_init_p ())
+    dcache_update_config (target_dcache);
+
   return target_dcache;
 }
 
@@ -54,7 +57,9 @@ target_dcache_get (void)
 DCACHE *
 target_dcache_get_or_init (void)
 {
-  if (!target_dcache_init_p ())
+  if (target_dcache_init_p ())
+    return target_dcache_get ();
+  else
     target_dcache = dcache_init ();
 
   return target_dcache;
-- 
1.7.7.6