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diff --git a/libglusterfs/src/gidcache.h b/libglusterfs/src/gidcache.h
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+/*
+ Copyright (c) 2008-2012 Red Hat, Inc. <http://www.redhat.com>
+ This file is part of GlusterFS.
+
+ This file is licensed to you under your choice of the GNU Lesser
+ General Public License, version 3 or any later version (LGPLv3 or
+ later), or the GNU General Public License, version 2 (GPLv2), in all
+ cases as published by the Free Software Foundation.
+*/
+
+#ifndef __GIDCACHE_H__
+#define __GIDCACHE_H__
+
+#include "glusterfs.h"
+#include "locking.h"
+
+/*
+ * TBD: make the cache size tunable
+ *
+ * The current size represents a pretty trivial amount of memory, and should
+ * provide good hit rates even for quite busy systems. If we ever want to
+ * support really large cache sizes, we'll need to do dynamic allocation
+ * instead of just defining an array within a private structure. It doesn't make
+ * a whole lot of sense to change the associativity, because it won't improve
+ * hit rates all that much and will increase the maintenance cost as we have
+ * to scan more entries with every lookup/update.
+ */
+
+#define AUX_GID_CACHE_ASSOC 4
+#define AUX_GID_CACHE_BUCKETS 256
+#define AUX_GID_CACHE_SIZE (AUX_GID_CACHE_ASSOC * AUX_GID_CACHE_BUCKETS)
+
+typedef struct {
+ uint64_t gl_id;
+ int gl_count;
+ gid_t *gl_list;
+ time_t gl_deadline;
+} gid_list_t;
+
+typedef struct {
+ gf_lock_t gc_lock;
+ uint32_t gc_max_age;
+ unsigned int gc_nbuckets;
+ gid_list_t gc_cache[AUX_GID_CACHE_SIZE];
+} gid_cache_t;
+
+int gid_cache_init(gid_cache_t *, uint32_t);
+const gid_list_t *gid_cache_lookup(gid_cache_t *, uint64_t);
+void gid_cache_release(gid_cache_t *, const gid_list_t *);
+int gid_cache_add(gid_cache_t *, gid_list_t *);
+
+#endif /* __GIDCACHE_H__ */