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authorunknown <guilhem@gbichot3.local>2007-02-28 17:50:51 +0100
committerunknown <guilhem@gbichot3.local>2007-02-28 17:50:51 +0100
commitea57b3d4a066a5507a7e322b53e3acab24a2855e (patch)
treea0703039f00da454a2a91c8b14835d45a6146209 /mysys/lf_alloc-pin.c
parentae72e394502e13b854b6e9bb00889fa6b69a7ed9 (diff)
parentfdf847fb62a0fcdf0edf25d6c8654b19eaa9a9ad (diff)
downloadmariadb-git-ea57b3d4a066a5507a7e322b53e3acab24a2855e.tar.gz
Merge gbichot3.local:/home/mysql_src/mysql-5.1-for-maria
into gbichot3.local:/home/mysql_src/mysql-maria BitKeeper/etc/ignore: auto-union BUILD/SETUP.sh: Auto merged client/mysqldump.c: Auto merged config/ac-macros/plugins.m4: Auto merged configure.in: Auto merged include/Makefile.am: Auto merged include/atomic/nolock.h: Auto merged include/atomic/rwlock.h: Auto merged include/atomic/x86-gcc.h: Auto merged include/atomic/x86-msvc.h: Auto merged include/ft_global.h: Auto merged include/keycache.h: Auto merged include/m_string.h: Auto merged include/my_atomic.h: Auto merged include/my_base.h: Auto merged include/my_dbug.h: Auto merged include/my_global.h: Auto merged include/my_handler.h: Auto merged include/my_sys.h: Auto merged include/myisam.h: Auto merged libmysql/CMakeLists.txt: Auto merged libmysqld/Makefile.am: Auto merged mysql-test/mysql-test-run.pl: Auto merged mysql-test/r/events_logs_tests.result: Auto merged mysql-test/t/events_logs_tests.test: Auto merged mysys/Makefile.am: Auto merged mysys/array.c: Auto merged mysys/mf_keycache.c: Auto merged mysys/mf_keycaches.c: Auto merged mysys/my_atomic.c: Auto merged mysys/my_bit.c: Auto merged mysys/my_bitmap.c: Auto merged mysys/my_create.c: Auto merged mysys/my_delete.c: Auto merged mysys/my_getsystime.c: Auto merged mysys/my_handler.c: Auto merged mysys/my_init.c: Auto merged mysys/my_open.c: Auto merged mysys/my_pread.c: Auto merged mysys/my_rename.c: Auto merged mysys/my_symlink.c: Auto merged mysys/my_sync.c: Auto merged plugin/daemon_example/daemon_example.cc: Auto merged sql/Makefile.am: Auto merged sql/filesort.cc: Auto merged sql/gen_lex_hash.cc: Auto merged sql/ha_ndbcluster.cc: Auto merged sql/handler.h: Auto merged sql/item_func.cc: Auto merged sql/item_func.h: Auto merged sql/log.cc: Auto merged sql/mysql_priv.h: Auto merged sql/set_var.h: Auto merged sql/sql_class.h: Auto merged sql/sql_parse.cc: Auto merged sql/sql_select.cc: Auto merged sql/sql_sort.h: Auto merged sql/sql_test.cc: Auto merged sql/uniques.cc: Auto merged sql/unireg.cc: Auto merged storage/Makefile.am: Auto merged storage/csv/ha_tina.cc: Auto merged storage/myisam/Makefile.am: Auto merged storage/myisam/ft_boolean_search.c: Auto merged storage/myisam/ft_nlq_search.c: Auto merged storage/myisam/ft_parser.c: Auto merged storage/myisam/ft_static.c: Auto merged storage/myisam/ft_stopwords.c: Auto merged storage/myisam/ft_update.c: Auto merged storage/myisam/fulltext.h: Auto merged storage/myisam/ha_myisam.h: Auto merged storage/myisam/mi_check.c: Auto merged storage/myisam/mi_create.c: Auto merged storage/myisam/mi_delete.c: Auto merged storage/myisam/mi_delete_all.c: Auto merged storage/myisam/mi_dynrec.c: Auto merged storage/myisam/mi_key.c: Auto merged storage/myisam/mi_log.c: Auto merged storage/myisam/mi_open.c: Auto merged storage/myisam/mi_packrec.c: Auto merged storage/myisam/mi_range.c: Auto merged storage/myisam/mi_rsamepos.c: Auto merged storage/myisam/mi_search.c: Auto merged storage/myisam/mi_test1.c: Auto merged storage/myisam/mi_test2.c: Auto merged storage/myisam/mi_unique.c: Auto merged storage/myisam/mi_update.c: Auto merged storage/myisam/mi_write.c: Auto merged storage/myisam/myisamchk.c: Auto merged storage/myisam/myisamlog.c: Auto merged storage/myisam/myisampack.c: Auto merged storage/myisam/rt_index.c: Auto merged storage/myisam/sort.c: Auto merged storage/myisammrg/ha_myisammrg.h: Auto merged unittest/mytap/tap.c: Auto merged mysql-test/r/view.result: manual merge mysql-test/t/view.test: manual merge Makefile.am: manual merge mysql-test/t/disabled.def: manual merge sql/mysqld.cc: manual merge sql/set_var.cc: manual merge sql/udf_example.c: manual merge storage/myisam/ha_myisam.cc: manual merge storage/myisam/myisamdef.h: manual merge storage/ndb/src/mgmapi/mgmapi.cpp: manual merge unittest/Makefile.am: manual merge unittest/mysys/Makefile.am: manual merge unittest/mysys/my_atomic-t.c: manual merge
Diffstat (limited to 'mysys/lf_alloc-pin.c')
-rw-r--r--mysys/lf_alloc-pin.c443
1 files changed, 443 insertions, 0 deletions
diff --git a/mysys/lf_alloc-pin.c b/mysys/lf_alloc-pin.c
new file mode 100644
index 00000000000..e964553a64c
--- /dev/null
+++ b/mysys/lf_alloc-pin.c
@@ -0,0 +1,443 @@
+/* QQ: TODO multi-pinbox */
+/* Copyright (C) 2000 MySQL AB
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
+
+/*
+ wait-free concurrent allocator based on pinning addresses
+
+ It works as follows: every thread (strictly speaking - every CPU, but
+ it's too difficult to do) has a small array of pointers. They're called
+ "pins". Before using an object its address must be stored in this array
+ (pinned). When an object is no longer necessary its address must be
+ removed from this array (unpinned). When a thread wants to free() an
+ object it scans all pins of all threads to see if somebody has this
+ object pinned. If yes - the object is not freed (but stored in a
+ "purgatory"). To reduce the cost of a single free() pins are not scanned
+ on every free() but only added to (thread-local) purgatory. On every
+ LF_PURGATORY_SIZE free() purgatory is scanned and all unpinned objects
+ are freed.
+
+ Pins are used to solve ABA problem. To use pins one must obey
+ a pinning protocol:
+ 1. Let's assume that PTR is a shared pointer to an object. Shared means
+ that any thread may modify it anytime to point to a different object
+ and free the old object. Later the freed object may be potentially
+ allocated by another thread. If we're unlucky that another thread may
+ set PTR to point to this object again. This is ABA problem.
+ 2. Create a local pointer LOCAL_PTR.
+ 3. Pin the PTR in a loop:
+ do
+ {
+ LOCAL_PTR= PTR;
+ pin(PTR, PIN_NUMBER);
+ } while (LOCAL_PTR != PTR)
+ 4. It is guaranteed that after the loop has ended, LOCAL_PTR
+ points to an object (or NULL, if PTR may be NULL), that
+ will never be freed. It is not guaranteed though
+ that LOCAL_PTR == PTR (as PTR can change any time)
+ 5. When done working with the object, remove the pin:
+ unpin(PIN_NUMBER)
+ 6. When copying pins (as in the list traversing loop:
+ pin(CUR, 1);
+ while ()
+ {
+ do // standard
+ { // pinning
+ NEXT=CUR->next; // loop
+ pin(NEXT, 0); // see #3
+ } while (NEXT != CUR->next); // above
+ ...
+ ...
+ CUR=NEXT;
+ pin(CUR, 1); // copy pin[0] to pin[1]
+ }
+ which keeps CUR address constantly pinned), note than pins may be
+ copied only upwards (!!!), that is pin[N] to pin[M], M > N.
+ 7. Don't keep the object pinned longer than necessary - the number of
+ pins you have is limited (and small), keeping an object pinned
+ prevents its reuse and cause unnecessary mallocs.
+
+ Implementation details:
+ Pins are given away from a "pinbox". Pinbox is stack-based allocator.
+ It used dynarray for storing pins, new elements are allocated by dynarray
+ as necessary, old are pushed in the stack for reuse. ABA is solved by
+ versioning a pointer - because we use an array, a pointer to pins is 32 bit,
+ upper 32 bits are used for a version.
+*/
+
+#include <my_global.h>
+#include <my_sys.h>
+#include <lf.h>
+
+#define LF_PINBOX_MAX_PINS 65536
+
+static void _lf_pinbox_real_free(LF_PINS *pins);
+
+/*
+ Initialize a pinbox. Normally called from lf_alloc_init.
+ See the latter for details.
+*/
+void lf_pinbox_init(LF_PINBOX *pinbox, uint free_ptr_offset,
+ lf_pinbox_free_func *free_func, void *free_func_arg)
+{
+ DBUG_ASSERT(sizeof(LF_PINS) == 128);
+ DBUG_ASSERT(free_ptr_offset % sizeof(void *) == 0);
+ lf_dynarray_init(&pinbox->pinstack, sizeof(LF_PINS));
+ pinbox->pinstack_top_ver= 0;
+ pinbox->pins_in_stack= 0;
+ pinbox->free_ptr_offset= free_ptr_offset;
+ pinbox->free_func= free_func;
+ pinbox->free_func_arg= free_func_arg;
+}
+
+void lf_pinbox_destroy(LF_PINBOX *pinbox)
+{
+ lf_dynarray_destroy(&pinbox->pinstack);
+}
+
+/*
+ Get pins from a pinbox. Usually called via lf_alloc_get_pins() or
+ lf_hash_get_pins().
+
+ DESCRIPTION
+ get a new LF_PINS structure from a stack of unused pins,
+ or allocate a new one out of dynarray.
+*/
+LF_PINS *_lf_pinbox_get_pins(LF_PINBOX *pinbox)
+{
+ uint32 pins, next, top_ver;
+ LF_PINS *el;
+
+ top_ver= pinbox->pinstack_top_ver;
+ do
+ {
+ if (!(pins= top_ver % LF_PINBOX_MAX_PINS))
+ {
+ pins= my_atomic_add32(&pinbox->pins_in_stack, 1)+1;
+ el= (LF_PINS *)_lf_dynarray_lvalue(&pinbox->pinstack, pins);
+ break;
+ }
+ el= (LF_PINS *)_lf_dynarray_value(&pinbox->pinstack, pins);
+ next= el->link;
+ } while (!my_atomic_cas32(&pinbox->pinstack_top_ver, &top_ver,
+ top_ver-pins+next+LF_PINBOX_MAX_PINS));
+ el->link= pins;
+ el->purgatory_count= 0;
+ el->pinbox= pinbox;
+ return el;
+}
+
+/*
+ Put pins back to a pinbox. Usually called via lf_alloc_put_pins() or
+ lf_hash_put_pins().
+
+ DESCRIPTION
+ empty the purgatory (XXX deadlock warning below!),
+ push LF_PINS structure to a stack
+*/
+void _lf_pinbox_put_pins(LF_PINS *pins)
+{
+ LF_PINBOX *pinbox= pins->pinbox;
+ uint32 top_ver, nr;
+ nr= pins->link;
+#ifdef MY_LF_EXTRA_DEBUG
+ {
+ int i;
+ for (i= 0; i < LF_PINBOX_PINS; i++)
+ DBUG_ASSERT(pins->pin[i] == 0);
+ }
+#endif
+ /*
+ XXX this will deadlock if other threads will wait for
+ the caller to do something after _lf_pinbox_put_pins(),
+ and they would have pinned addresses that the caller wants to free.
+ Thus: only free pins when all work is done and nobody can wait for you!!!
+ */
+ while (pins->purgatory_count)
+ {
+ _lf_pinbox_real_free(pins);
+ if (pins->purgatory_count)
+ {
+ my_atomic_rwlock_wrunlock(&pins->pinbox->pinstack.lock);
+ pthread_yield();
+ my_atomic_rwlock_wrlock(&pins->pinbox->pinstack.lock);
+ }
+ }
+ top_ver= pinbox->pinstack_top_ver;
+ if (nr == pinbox->pins_in_stack)
+ {
+ int32 tmp= nr;
+ if (my_atomic_cas32(&pinbox->pins_in_stack, &tmp, tmp-1))
+ goto ret;
+ }
+
+ do
+ {
+ pins->link= top_ver % LF_PINBOX_MAX_PINS;
+ } while (!my_atomic_cas32(&pinbox->pinstack_top_ver, &top_ver,
+ top_ver-pins->link+nr+LF_PINBOX_MAX_PINS));
+ret:
+ return;
+}
+
+static int ptr_cmp(void **a, void **b)
+{
+ return *a < *b ? -1 : *a == *b ? 0 : 1;
+}
+
+#define add_to_purgatory(PINS, ADDR) \
+ do \
+ { \
+ *(void **)((char *)(ADDR)+(PINS)->pinbox->free_ptr_offset)= \
+ (PINS)->purgatory; \
+ (PINS)->purgatory= (ADDR); \
+ (PINS)->purgatory_count++; \
+ } while (0)
+
+/*
+ Free an object allocated via pinbox allocator
+
+ DESCRIPTION
+ add an object to purgatory. if necessary, call _lf_pinbox_real_free()
+ to actually free something.
+*/
+void _lf_pinbox_free(LF_PINS *pins, void *addr)
+{
+ add_to_purgatory(pins, addr);
+ if (pins->purgatory_count % LF_PURGATORY_SIZE)
+ _lf_pinbox_real_free(pins);
+}
+
+struct st_harvester {
+ void **granary;
+ int npins;
+};
+
+/*
+ callback for _lf_dynarray_iterate:
+ scan all pins or all threads and accumulate all pins
+*/
+static int harvest_pins(LF_PINS *el, struct st_harvester *hv)
+{
+ int i;
+ LF_PINS *el_end= el+min(hv->npins, LF_DYNARRAY_LEVEL_LENGTH);
+ for (; el < el_end; el++)
+ {
+ for (i= 0; i < LF_PINBOX_PINS; i++)
+ {
+ void *p= el->pin[i];
+ if (p)
+ *hv->granary++= p;
+ }
+ }
+ hv->npins-= LF_DYNARRAY_LEVEL_LENGTH;
+ return 0;
+}
+
+/*
+ callback for _lf_dynarray_iterate:
+ scan all pins or all threads and see if addr is present there
+*/
+static int match_pins(LF_PINS *el, void *addr)
+{
+ int i;
+ LF_PINS *el_end= el+LF_DYNARRAY_LEVEL_LENGTH;
+ for (; el < el_end; el++)
+ for (i= 0; i < LF_PINBOX_PINS; i++)
+ if (el->pin[i] == addr)
+ return 1;
+ return 0;
+}
+
+/*
+ Scan the purgatory as free everything that can be freed
+*/
+static void _lf_pinbox_real_free(LF_PINS *pins)
+{
+ int npins;
+ void *list;
+ void **addr;
+ LF_PINBOX *pinbox= pins->pinbox;
+
+ npins= pinbox->pins_in_stack+1;
+
+#ifdef HAVE_ALLOCA
+ /* create a sorted list of pinned addresses, to speed up searches */
+ if (sizeof(void *)*LF_PINBOX_PINS*npins < my_thread_stack_size)
+ {
+ struct st_harvester hv;
+ addr= (void **) alloca(sizeof(void *)*LF_PINBOX_PINS*npins);
+ hv.granary= addr;
+ hv.npins= npins;
+ /* scan the dynarray and accumulate all pinned addresses */
+ _lf_dynarray_iterate(&pinbox->pinstack,
+ (lf_dynarray_func)harvest_pins, &hv);
+
+ npins= hv.granary-addr;
+ /* and sort them */
+ if (npins)
+ qsort(addr, npins, sizeof(void *), (qsort_cmp)ptr_cmp);
+ }
+ else
+#endif
+ addr= 0;
+
+ list= pins->purgatory;
+ pins->purgatory= 0;
+ pins->purgatory_count= 0;
+ while (list)
+ {
+ void *cur= list;
+ list= *(void **)((char *)cur+pinbox->free_ptr_offset);
+ if (npins)
+ {
+ if (addr) /* use binary search */
+ {
+ void **a, **b, **c;
+ for (a= addr, b= addr+npins-1, c= a+(b-a)/2; b-a>1; c= a+(b-a)/2)
+ if (cur == *c)
+ a= b= c;
+ else if (cur > *c)
+ a= c;
+ else
+ b= c;
+ if (cur == *a || cur == *b)
+ goto found;
+ }
+ else /* no alloca - no cookie. linear search here */
+ {
+ if (_lf_dynarray_iterate(&pinbox->pinstack,
+ (lf_dynarray_func)match_pins, cur))
+ goto found;
+ }
+ }
+ /* not pinned - freeing */
+ pinbox->free_func(cur, pinbox->free_func_arg);
+ continue;
+found:
+ /* pinned - keeping */
+ add_to_purgatory(pins, cur);
+ }
+}
+
+/*
+ callback for _lf_pinbox_real_free to free an unpinned object -
+ add it back to the allocator stack
+*/
+static void alloc_free(struct st_lf_alloc_node *node, LF_ALLOCATOR *allocator)
+{
+ struct st_lf_alloc_node *tmp;
+ tmp= allocator->top;
+ do
+ {
+ node->next= tmp;
+ } while (!my_atomic_casptr((void **)&allocator->top, (void **)&tmp, node) &&
+ LF_BACKOFF);
+}
+
+/* lock-free memory allocator for fixed-size objects */
+
+LF_REQUIRE_PINS(1);
+
+/*
+ initialize lock-free allocatod.
+
+ SYNOPSYS
+ allocator -
+ size a size of an object to allocate
+ free_ptr_offset an offset inside the object to a sizeof(void *)
+ memory that is guaranteed to be unused after
+ the object is put in the purgatory. Unused by ANY
+ thread, not only the purgatory owner.
+*/
+void lf_alloc_init(LF_ALLOCATOR *allocator, uint size, uint free_ptr_offset)
+{
+ lf_pinbox_init(&allocator->pinbox, free_ptr_offset,
+ (lf_pinbox_free_func *)alloc_free, allocator);
+ allocator->top= 0;
+ allocator->mallocs= 0;
+ allocator->element_size= size;
+ DBUG_ASSERT(size >= (int)sizeof(void *));
+ DBUG_ASSERT(free_ptr_offset < size);
+}
+
+/*
+ destroy the allocator, free everything that's in it
+*/
+void lf_alloc_destroy(LF_ALLOCATOR *allocator)
+{
+ struct st_lf_alloc_node *node= allocator->top;
+ while (node)
+ {
+ struct st_lf_alloc_node *tmp= node->next;
+ my_free((void *)node, MYF(0));
+ node= tmp;
+ }
+ lf_pinbox_destroy(&allocator->pinbox);
+ allocator->top= 0;
+}
+
+/*
+ Allocate and return an new object.
+
+ DESCRIPTION
+ Pop an unused object from the stack or malloc it is the stack is empty.
+ pin[0] is used, it's removed on return.
+*/
+void *_lf_alloc_new(LF_PINS *pins)
+{
+ LF_ALLOCATOR *allocator= (LF_ALLOCATOR *)(pins->pinbox->free_func_arg);
+ struct st_lf_alloc_node *node;
+ for (;;)
+ {
+ do
+ {
+ node= allocator->top;
+ _lf_pin(pins, 0, node);
+ } while (node != allocator->top && LF_BACKOFF);
+ if (!node)
+ {
+ if (!(node= (void *)my_malloc(allocator->element_size,
+ MYF(MY_WME|MY_ZEROFILL))))
+ break;
+#ifdef MY_LF_EXTRA_DEBUG
+ my_atomic_add32(&allocator->mallocs, 1);
+#endif
+ break;
+ }
+ if (my_atomic_casptr((void **)&allocator->top,
+ (void *)&node, *(void **)node))
+ break;
+ }
+ _lf_unpin(pins, 0);
+ return node;
+}
+
+/*
+ count the number of objects in a pool.
+
+ NOTE
+ This is NOT thread-safe !!!
+*/
+uint lf_alloc_in_pool(LF_ALLOCATOR *allocator)
+{
+ uint i;
+ struct st_lf_alloc_node *node;
+ for (node= allocator->top, i= 0; node; node= node->next, i++)
+ /* no op */;
+ return i;
+}
+