PLPA Users' Mailing List Archives

Subject: [PLPA users] [PATCH 4/5] shift away common zeros of socket_ids to reduce socket arrays
From: Bert Wesarg (bert.wesarg_at_[hidden])
Date: 2009-07-23 17:47:49

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• In reply to: Bert Wesarg: "[PLPA users] [PATCH 0/5] Greatly reduce memory needs for socket arrays"
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---
 src/libplpa/plpa_map.c |   23 ++++++++++++++++++-----
 1 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/src/libplpa/plpa_map.c b/src/libplpa/plpa_map.c
index d3e8f62..8882782 100644
--- a/src/libplpa/plpa_map.c
+++ b/src/libplpa/plpa_map.c
@@ -127,6 +127,7 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <stdbool.h>
+#include <strings.h>
 
 typedef struct tuple_t_ {
     int processor_id, socket_id, core_id, online;
@@ -140,6 +141,7 @@ static int num_sockets = -1;
 static int min_socket_id = INT_MAX;
 static int max_socket_id = -1;
 static int socket_index_extent = 0;
+static int socket_index_shift = 0;
 static int *max_core_id = NULL;
 static int *num_cores = NULL;
 static int max_core_id_overall = -1;
@@ -149,12 +151,12 @@ static PLPA_NAME(cache_behavior_t) cache_behavior = PLPA_NAME_CAPS(CACHE_IGNORE)
 
 static inline int socket_id_to_index(int socket_id)
 {
-    return socket_id - min_socket_id;
+    return (socket_id - min_socket_id) >> socket_index_shift;
 }
 
 static inline int socket_index_to_id(int socket_index)
 {
-    return socket_index + min_socket_id;
+    return (socket_index << socket_index_shift) + min_socket_id;
 }
 
 static void clear_cache(void)
@@ -179,13 +181,13 @@ static void clear_cache(void)
     num_processors = max_processor_id = -1;
     num_sockets = max_socket_id = -1;
     min_socket_id = INT_MAX;
-    socket_index_extent = 0;
+    socket_index_extent = socket_index_shift = 0;
     max_core_id_overall = -1;
 }
 
 static void load_cache(void)
 {
-    int i, j, k, invalid_entry, fd, found_online;
+    int i, j, k, invalid_entry, fd, found_online, socket_or;
     char path[PATH_MAX], buf[8];
     PLPA_NAME(cpu_set_t) valid_processors;
     PLPA_NAME(cpu_set_t) *cores_on_sockets;
@@ -272,6 +274,7 @@ static void load_cache(void)
     map_processor_id_to_tuple[invalid_entry].core_id = -1;
 
     /* Build a cached map of (socket,core) tuples */
+    socket_or = 0;
     for (found = 0, i = 0; i <= max_processor_id; ++i) {
 
         /* Check for invalid processor ID */
@@ -354,6 +357,10 @@ static void load_cache(void)
         if (map_processor_id_to_tuple[i].socket_id < min_socket_id) {
             min_socket_id = map_processor_id_to_tuple[i].socket_id;
         }
+
+        /* collect all set bits in any socket_id, to shift away common
+           trailing zeros */
+        socket_or |= map_processor_id_to_tuple[i].socket_id;
     }
 
     /* If we didn't find any core_id/physical_package_id's, then we
@@ -363,8 +370,14 @@ static void load_cache(void)
         return;
     }
 
+    /* don't do any shifting if negative numbers are involved */
+    if (socket_or > 0) {
+        /* we shift away common trailing zeros */
+        socket_index_shift = ffs(socket_or) - 1;
+    }
     /* index range for sockets, [0, socket_index_extent) */
-    socket_index_extent = max_socket_id - min_socket_id + 1;
+    socket_index_extent =
+        ((max_socket_id - min_socket_id) >> socket_index_shift) + 1;
 
     /* Now that we know the max number of sockets, allocate some
        arrays */
-- 
1.6.3.3.618.gce7bf

• Next message: Bert Wesarg: "[PLPA users] [PATCH 5/5] introduce get_socket_info3() to get also the min_socket_id"
• Previous message: Bert Wesarg: "[PLPA users] [PATCH 3/5] introduce min_socket_id to remove empty gap in socket arrays"
• In reply to: Bert Wesarg: "[PLPA users] [PATCH 0/5] Greatly reduce memory needs for socket arrays"
• Next in thread: Bert Wesarg: "[PLPA users] [PATCH 5/5] introduce get_socket_info3() to get also the min_socket_id"