diff options
Diffstat (limited to 'debian/patches/0004-ipc-replace-reverse-hash-table-with-a-radix-tree.patch')
| -rw-r--r-- | debian/patches/0004-ipc-replace-reverse-hash-table-with-a-radix-tree.patch | 427 |
1 files changed, 427 insertions, 0 deletions
diff --git a/debian/patches/0004-ipc-replace-reverse-hash-table-with-a-radix-tree.patch b/debian/patches/0004-ipc-replace-reverse-hash-table-with-a-radix-tree.patch new file mode 100644 index 0000000..208f98a --- /dev/null +++ b/debian/patches/0004-ipc-replace-reverse-hash-table-with-a-radix-tree.patch @@ -0,0 +1,427 @@ +From c4f001006532204fbfa504dd99a50da784e0505f Mon Sep 17 00:00:00 2001 +From: Justus Winter <4winter@informatik.uni-hamburg.de> +Date: Wed, 18 Mar 2015 12:25:26 +0100 +Subject: [PATCH gnumach 4/7] ipc: replace reverse hash table with a radix tree + +Currently, there is a hash table mapping (space, object) tuples to +`ipc_entry' objects. This hash table is intertwined with the IPC +tables. There is one hash table per IPC space, but it is only for the +entries in the IPC table. This hash table is called `local' in the +source. + +All IPC entries being spilled into the splay tree are instead mapped +by a global hash table. + +Replace the local (i.e. per IPC space) reverse hash table with a radix +tree. + +* ipc/ipc_entry.c (ipc_entry_grow_table): Adjust accordingly. +* ipc/ipc_entry.h (struct ipc_entry): Adjust comment. +* ipc/ipc_hash.c: Adjust comment explaining the local lookup table. +(IPC_LOCAL_HASH_INVARIANT): New macro. +(ipc_hash_local_lookup): Use the new `ipc_reverse_lookup' function. +(ipc_hash_local_insert): Use the new `ipc_reverse_insert' function. +(ipc_hash_local_delete): Use the new `ipc_reverse_remove' function. +* ipc/ipc_space.c (ipc_space_create): Initialize radix tree. +(ipc_space_destroy): Free radix tree. +* ipc/ipc_space.h (struct ipc_space): Add radix tree. +(ipc_reverse_insert): New function. +(ipc_reverse_remove): Likewise. +(ipc_reverse_remove_all): Likewise. +(ipc_reverse_lookup): Likewise. +--- + ipc/ipc_entry.c | 5 +- + ipc/ipc_entry.h | 5 -- + ipc/ipc_hash.c | 184 ++++++++------------------------------------------------ + ipc/ipc_space.c | 3 + + ipc/ipc_space.h | 63 +++++++++++++++++++ + 5 files changed, 93 insertions(+), 167 deletions(-) + +diff --git a/ipc/ipc_entry.c b/ipc/ipc_entry.c +index e78f74e..5b9fd98 100644 +--- a/ipc/ipc_entry.c ++++ b/ipc/ipc_entry.c +@@ -618,6 +618,7 @@ ipc_entry_grow_table(ipc_space_t space) + is_write_unlock(space); + thread_wakeup((event_t) space); + it_entries_free(its, table); ++ ipc_reverse_remove_all(space); + is_write_lock(space); + return KERN_SUCCESS; + } +@@ -641,9 +642,6 @@ ipc_entry_grow_table(ipc_space_t space) + memcpy(table, otable, + osize * sizeof(struct ipc_entry)); + +- for (i = 0; i < osize; i++) +- table[i].ie_index = 0; +- + (void) memset((void *) (table + osize), 0, + (size - osize) * sizeof(struct ipc_entry)); + +@@ -651,6 +649,7 @@ ipc_entry_grow_table(ipc_space_t space) + * Put old entries into the reverse hash table. + */ + ++ ipc_reverse_remove_all(space); + for (i = 0; i < osize; i++) { + ipc_entry_t entry = &table[i]; + +diff --git a/ipc/ipc_entry.h b/ipc/ipc_entry.h +index cb6d3f9..0caa70b 100644 +--- a/ipc/ipc_entry.h ++++ b/ipc/ipc_entry.h +@@ -54,11 +54,6 @@ + * those entries. The cutoff point between the table and the tree + * is adjusted dynamically to minimize memory consumption. + * +- * The ie_index field of entries in the table implements +- * a ordered hash table with open addressing and linear probing. +- * This hash table converts (space, object) -> name. +- * It is used independently of the other fields. +- * + * Free (unallocated) entries in the table have null ie_object + * fields. The ie_bits field is zero except for IE_BITS_GEN. + * The ie_next (ie_request) field links free entries into a free list. +diff --git a/ipc/ipc_hash.c b/ipc/ipc_hash.c +index c2c6d6e..87952a7 100644 +--- a/ipc/ipc_hash.c ++++ b/ipc/ipc_hash.c +@@ -296,37 +296,19 @@ ipc_hash_global_delete( + } + + /* +- * Each space has a local reverse hash table, which holds +- * entries from the space's table. In fact, the hash table +- * just uses a field (ie_index) in the table itself. +- * +- * The local hash table is an open-addressing hash table, +- * which means that when a collision occurs, instead of +- * throwing the entry into a bucket, the entry is rehashed +- * to another position in the table. In this case the rehash +- * is very simple: linear probing (ie, just increment the position). +- * This simple rehash makes deletions tractable (they're still a pain), +- * but it means that collisions tend to build up into clumps. +- * +- * Because at least one entry in the table (index 0) is always unused, +- * there will always be room in the reverse hash table. If a table +- * with n slots gets completely full, the reverse hash table will +- * have one giant clump of n-1 slots and one free slot somewhere. +- * Because entries are only entered into the reverse table if they +- * are pure send rights (not receive, send-once, port-set, +- * or dead-name rights), and free entries of course aren't entered, +- * I expect the reverse hash table won't get unreasonably full. +- * +- * Ordered hash tables (Amble & Knuth, Computer Journal, v. 17, no. 2, +- * pp. 135-142.) may be desirable here. They can dramatically help +- * unsuccessful lookups. But unsuccessful lookups are almost always +- * followed by insertions, and those slow down somewhat. They +- * also can help deletions somewhat. Successful lookups aren't affected. +- * So possibly a small win; probably nothing significant. ++ * Each space has a local reverse mapping from objects to entries ++ * from the space's table. This used to be a hash table. + */ + +-#define IH_LOCAL_HASH(obj, size) \ +- ((((mach_port_index_t) (vm_offset_t) (obj)) >> 6) & (size - 1)) ++#define IPC_LOCAL_HASH_INVARIANT(S, O, N, E) \ ++ MACRO_BEGIN \ ++ assert(IE_BITS_TYPE((E)->ie_bits) == MACH_PORT_TYPE_SEND || \ ++ IE_BITS_TYPE((E)->ie_bits) == MACH_PORT_TYPE_SEND_RECEIVE || \ ++ IE_BITS_TYPE((E)->ie_bits) == MACH_PORT_TYPE_NONE); \ ++ assert((E)->ie_object == (O)); \ ++ assert((E)->ie_index == (N)); \ ++ assert(&(S)->is_table[N] == (E)); \ ++ MACRO_END + + /* + * Routine: ipc_hash_local_lookup +@@ -345,37 +327,15 @@ ipc_hash_local_lookup( + mach_port_t *namep, + ipc_entry_t *entryp) + { +- ipc_entry_t table; +- ipc_entry_num_t size; +- mach_port_index_t hindex, index; +- + assert(space != IS_NULL); + assert(obj != IO_NULL); + +- table = space->is_table; +- size = space->is_table_size; +- hindex = IH_LOCAL_HASH(obj, size); +- +- /* +- * Ideally, table[hindex].ie_index is the name we want. +- * However, must check ie_object to verify this, +- * because collisions can happen. In case of a collision, +- * search farther along in the clump. +- */ +- +- while ((index = table[hindex].ie_index) != 0) { +- ipc_entry_t entry = &table[index]; +- +- if (entry->ie_object == obj) { +- *namep = MACH_PORT_MAKEB(index, entry->ie_bits); +- *entryp = entry; +- return TRUE; +- } +- +- if (++hindex == size) +- hindex = 0; ++ *entryp = ipc_reverse_lookup(space, obj); ++ if (*entryp != IE_NULL) { ++ *namep = (*entryp)->ie_index; ++ IPC_LOCAL_HASH_INVARIANT(space, obj, *namep, *entryp); ++ return TRUE; + } +- + return FALSE; + } + +@@ -394,33 +354,15 @@ ipc_hash_local_insert( + mach_port_index_t index, + ipc_entry_t entry) + { +- ipc_entry_t table; +- ipc_entry_num_t size; +- mach_port_index_t hindex; +- ++ kern_return_t kr; + assert(index != 0); + assert(space != IS_NULL); + assert(obj != IO_NULL); + +- table = space->is_table; +- size = space->is_table_size; +- hindex = IH_LOCAL_HASH(obj, size); +- +- assert(entry == &table[index]); +- assert(entry->ie_object == obj); +- +- /* +- * We want to insert at hindex, but there may be collisions. +- * If a collision occurs, search for the end of the clump +- * and insert there. +- */ +- +- while (table[hindex].ie_index != 0) { +- if (++hindex == size) +- hindex = 0; +- } +- +- table[hindex].ie_index = index; ++ entry->ie_index = index; ++ IPC_LOCAL_HASH_INVARIANT(space, obj, index, entry); ++ kr = ipc_reverse_insert(space, obj, entry); ++ assert(kr == 0); + } + + /* +@@ -438,90 +380,14 @@ ipc_hash_local_delete( + mach_port_index_t index, + ipc_entry_t entry) + { +- ipc_entry_t table; +- ipc_entry_num_t size; +- mach_port_index_t hindex, dindex; +- ++ ipc_entry_t removed; + assert(index != MACH_PORT_NULL); + assert(space != IS_NULL); + assert(obj != IO_NULL); + +- table = space->is_table; +- size = space->is_table_size; +- hindex = IH_LOCAL_HASH(obj, size); +- +- assert(entry == &table[index]); +- assert(entry->ie_object == obj); +- +- /* +- * First check we have the right hindex for this index. +- * In case of collision, we have to search farther +- * along in this clump. +- */ +- +- while (table[hindex].ie_index != index) { +- if (table[hindex].ie_index == 0) +- { +- static int gak = 0; +- if (gak == 0) +- { +- printf("gak! entry wasn't in hash table!\n"); +- gak = 1; +- } +- return; +- } +- if (++hindex == size) +- hindex = 0; +- } +- +- /* +- * Now we want to set table[hindex].ie_index = 0. +- * But if we aren't the last index in a clump, +- * this might cause problems for lookups of objects +- * farther along in the clump that are displaced +- * due to collisions. Searches for them would fail +- * at hindex instead of succeeding. +- * +- * So we must check the clump after hindex for objects +- * that are so displaced, and move one up to the new hole. +- * +- * hindex - index of new hole in the clump +- * dindex - index we are checking for a displaced object +- * +- * When we move a displaced object up into the hole, +- * it creates a new hole, and we have to repeat the process +- * until we get to the end of the clump. +- */ +- +- for (dindex = hindex; index != 0; hindex = dindex) { +- for (;;) { +- mach_port_index_t tindex; +- ipc_object_t tobj; +- +- if (++dindex == size) +- dindex = 0; +- assert(dindex != hindex); +- +- /* are we at the end of the clump? */ +- +- index = table[dindex].ie_index; +- if (index == 0) +- break; +- +- /* is this a displaced object? */ +- +- tobj = table[index].ie_object; +- assert(tobj != IO_NULL); +- tindex = IH_LOCAL_HASH(tobj, size); +- +- if ((dindex < hindex) ? +- ((dindex < tindex) && (tindex <= hindex)) : +- ((dindex < tindex) || (tindex <= hindex))) +- break; +- } +- +- table[hindex].ie_index = index; +- } ++ IPC_LOCAL_HASH_INVARIANT(space, obj, index, entry); ++ removed = ipc_reverse_remove(space, obj); ++ assert(removed == entry); + } + + /* +diff --git a/ipc/ipc_space.c b/ipc/ipc_space.c +index ab55e83..dcc96b3 100644 +--- a/ipc/ipc_space.c ++++ b/ipc/ipc_space.c +@@ -148,6 +148,7 @@ ipc_space_create( + space->is_tree_total = 0; + space->is_tree_small = 0; + space->is_tree_hash = 0; ++ rdxtree_init(&space->is_reverse_map); + + *spacep = space; + return KERN_SUCCESS; +@@ -271,6 +272,8 @@ ipc_space_destroy( + } + ipc_splay_traverse_finish(&space->is_tree); + ++ rdxtree_remove_all(&space->is_reverse_map); ++ + /* + * Because the space is now dead, + * we must release the "active" reference for it. +diff --git a/ipc/ipc_space.h b/ipc/ipc_space.h +index c4683d2..04eb0dd 100644 +--- a/ipc/ipc_space.h ++++ b/ipc/ipc_space.h +@@ -42,8 +42,10 @@ + #include <mach/boolean.h> + #include <mach/kern_return.h> + #include <mach/mach_types.h> ++#include <machine/vm_param.h> + #include <kern/macro_help.h> + #include <kern/lock.h> ++#include <kern/rdxtree.h> + #include <kern/slab.h> + #include <ipc/ipc_splay.h> + #include <ipc/ipc_types.h> +@@ -79,6 +81,8 @@ struct ipc_space { + ipc_entry_num_t is_tree_total; /* number of entries in the tree */ + ipc_entry_num_t is_tree_small; /* # of small entries in the tree */ + ipc_entry_num_t is_tree_hash; /* # of hashed entries in the tree */ ++ struct rdxtree is_reverse_map; /* maps objects to entries */ ++ + }; + + #define IS_NULL ((ipc_space_t) 0) +@@ -135,4 +139,63 @@ kern_return_t ipc_space_create(ipc_table_size_t, ipc_space_t *); + kern_return_t ipc_space_create_special(struct ipc_space **); + void ipc_space_destroy(struct ipc_space *); + ++/* Reverse lookups. */ ++ ++/* Cast a pointer to a suitable key. */ ++#define KEY(X) \ ++ ({ \ ++ assert((((unsigned long) (X)) & 0x07) == 0); \ ++ ((unsigned long long) \ ++ (((unsigned long) (X) - VM_MIN_KERNEL_ADDRESS) >> 3)); \ ++ }) ++ ++/* Insert (OBJ, ENTRY) pair into the reverse mapping. SPACE must ++ be write-locked. */ ++static inline kern_return_t ++ipc_reverse_insert(ipc_space_t space, ++ ipc_object_t obj, ++ ipc_entry_t entry) ++{ ++ assert(space != IS_NULL); ++ assert(obj != IO_NULL); ++ return (kern_return_t) rdxtree_insert(&space->is_reverse_map, ++ KEY(obj), entry); ++} ++ ++/* Remove OBJ from the reverse mapping. SPACE must be ++ write-locked. */ ++static inline ipc_entry_t ++ipc_reverse_remove(ipc_space_t space, ++ ipc_object_t obj) ++{ ++ assert(space != IS_NULL); ++ assert(obj != IO_NULL); ++ return rdxtree_remove(&space->is_reverse_map, KEY(obj)); ++} ++ ++/* Remove all entries from the reverse mapping. SPACE must be ++ write-locked. */ ++static inline void ++ipc_reverse_remove_all(ipc_space_t space) ++{ ++ assert(space != IS_NULL); ++ rdxtree_remove_all(&space->is_reverse_map); ++ assert(space->is_reverse_map.height == 0); ++ assert(space->is_reverse_map.root == NULL); ++} ++ ++/* Return ENTRY related to OBJ, or NULL if no such entry is found in ++ the reverse mapping. SPACE must be read-locked or ++ write-locked. */ ++static inline ipc_entry_t ++ipc_reverse_lookup(ipc_space_t space, ++ ipc_object_t obj) ++{ ++ assert(space != IS_NULL); ++ assert(obj != IO_NULL); ++ return rdxtree_lookup(&space->is_reverse_map, KEY(obj)); ++} ++ ++#undef KEY ++ + #endif /* _IPC_IPC_SPACE_H_ */ +-- +2.1.4 + |