Author: stefan2
Date: Fri Mar 7 22:11:24 2014
New Revision: 1575428
URL: http://svn.apache.org/r1575428
Log:
In FSFS, remove padding from cache key structs to simplify handling.
Also, document why we want them to be 16 bytes whenever we can help it.
* subversion/libsvn_fs_fs/fs.h
(pair_cache_key_t): Widen revision type to eliminate padding on
platforms with sizeof(long) != 8. Document the
struct size rationale.
(window_cache_key_t): Document the struct size rationale.
Modified:
subversion/trunk/subversion/libsvn_fs_fs/fs.h
Modified: subversion/trunk/subversion/libsvn_fs_fs/fs.h
URL:
http://svn.apache.org/viewvc/subversion/trunk/subversion/libsvn_fs_fs/fs.h?rev=1575428&r1=1575427&r2=1575428&view=diff
==============================================================================
--- subversion/trunk/subversion/libsvn_fs_fs/fs.h (original)
+++ subversion/trunk/subversion/libsvn_fs_fs/fs.h Fri Mar 7 22:11:24 2014
@@ -254,20 +254,27 @@ typedef struct fs_fs_dag_cache_t fs_fs_d
/* Key type for all caches that use revision + offset / counter as key.
- NOTE: always initialize this using calloc() or '= {0};'! This is used
- as a cache key and the padding bytes on 32 bit archs should be zero for
- cache effectiveness. */
+ Note: Cache keys should be 16 bytes for best performance and there
+ should be no padding. */
typedef struct pair_cache_key_t
{
- svn_revnum_t revision;
+ /* The object's revision. Use the 64 data type to prevent padding. */
+ apr_int64_t revision;
+ /* Sub-address: item index, revprop generation, packed flag, etc. */
apr_int64_t second;
} pair_cache_key_t;
-/* Key type that identifies a txdelta window. */
+/* Key type that identifies a txdelta window.
+
+ Note: Cache keys should be 16 bytes for best performance and there
+ should be no padding. */
typedef struct window_cache_key_t
{
- /* Revision that contains the representation */
+ /* Revision that contains the representation.
+ We limit this to 32 bit because it revision numbers are practically
+ limited to 32 bits by the RA layer, ATM, and we want to keep this
+ struct 16 bytes long. */
apr_uint32_t revision;
/* Window number within that representation */
