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PS-314: issue with 65536+ threads and mdl locks #19

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Feb 22, 2018
Merged

PS-314: issue with 65536+ threads and mdl locks #19

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12 changes: 6 additions & 6 deletions include/lf.h
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Original file line number Diff line number Diff line change
Expand Up @@ -78,19 +78,19 @@ typedef struct {
lf_pinbox_free_func *free_func;
void *free_func_arg;
uint free_ptr_offset;
std::atomic<uint32> pinstack_top_ver; /* this is a versioned pointer */
std::atomic<uint32> pins_in_array; /* number of elements in array */
std::atomic<uint64> pinstack_top_ver; /* this is a versioned pointer */
std::atomicuint64> pins_in_array; /* number of elements in array */
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Compilation-breaking typo

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Uhh, sorry about that, I thought I compiled my last version of this before pushing :(

} LF_PINBOX;

typedef struct st_lf_pins {
std::atomic<void *> pin[LF_PINBOX_PINS];
LF_PINBOX *pinbox;
void *purgatory;
uint32 purgatory_count;
std::atomic<uint32> link;
uint64 purgatory_count;
std::atomic<uint64> link;
/* we want sizeof(LF_PINS) to be 64 to avoid false sharing */
#if SIZEOF_INT*2+SIZEOF_CHARP*(LF_PINBOX_PINS+2) != 64
char pad[64-sizeof(uint32)*2-sizeof(void*)*(LF_PINBOX_PINS+2)];
#if 2*8+SIZEOF_CHARP*(LF_PINBOX_PINS+2) != 64
char pad[64-sizeof(uint64)*2-sizeof(void*)*(LF_PINBOX_PINS+2)];
#endif
} LF_PINS;

Expand Down
16 changes: 8 additions & 8 deletions mysys/lf_alloc-pin.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -114,8 +114,8 @@ static_assert(
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 16 bit,
upper 16 bits are used for a version.
versioning a pointer - because we use an array, a pointer to pins is 32 bit,
upper 32 bits are used for a version.
*/
#include "lf.h"
#include "my_atomic.h"
Expand All @@ -127,7 +127,7 @@ static_assert(
#include "mysql/service_mysql_alloc.h"
#include "mysys/mysys_priv.h" /* key_memory_lf_node */

#define LF_PINBOX_MAX_PINS 65536
#define LF_PINBOX_MAX_PINS (65536ULL*65536ULL)

static void lf_pinbox_real_free(LF_PINS *pins);

Expand Down Expand Up @@ -165,15 +165,15 @@ void lf_pinbox_destroy(LF_PINBOX *pinbox)
*/
LF_PINS *lf_pinbox_get_pins(LF_PINBOX *pinbox)
{
uint32 pins, next, top_ver;
uint64 pins, next, top_ver;
LF_PINS *el;
/*
We have an array of max. 64k elements.
The highest index currently allocated is pinbox->pins_in_array.
Freed elements are in a lifo stack, pinstack_top_ver.
pinstack_top_ver is 32 bits; 16 low bits are the index in the
array, to the first element of the list. 16 high bits are a version
(every time the 16 low bits are updated, the 16 high bits are
pinstack_top_ver is 64 bits; 16 low bits are the index in the
array, to the first element of the list. 32 high bits are a version
(every time the 32 low bits are updated, the 32 high bits are
incremented). Versioning prevents the ABA problem.
*/
top_ver= pinbox->pinstack_top_ver;
Expand Down Expand Up @@ -221,7 +221,7 @@ LF_PINS *lf_pinbox_get_pins(LF_PINBOX *pinbox)
void lf_pinbox_put_pins(LF_PINS *pins)
{
LF_PINBOX *pinbox= pins->pinbox;
uint32 top_ver, nr;
uint64 top_ver, nr;
nr= pins->link;

#ifndef DBUG_OFF
Expand Down