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[commtech] BatchQueue v2

Uses 2 mapping to the same structure to avoid prefetching of the
producer semi-buffer by the consumer. The idea is to access everything
through mapping 1 except semi-buffer 2 which is accessed through mapping
2.
rebased_bqv2_avoid_if
Thomas Preud'homme 10 years ago
committed by Thomas Preud'homme
parent
commit
a20c9a8a21
4 changed files with 165 additions and 37 deletions
  1. +1
    -1
      communication_techniques/Makefile
  2. +48
    -6
      communication_techniques/include/batch_queue_common_comm.h
  3. +114
    -29
      communication_techniques/src/communication/batch_queue.c
  4. +2
    -1
      communication_techniques/src/main.c

+ 1
- 1
communication_techniques/Makefile View File

@ -14,7 +14,7 @@ COMMDIR:=communication
# I know -finline-functions and -finline-functions-called-once are enabled by
# -O3 but I did this in case gcc behaviour change one day
CFLAGS:=-c -O3 -finline-functions -finline-functions-called-once -Wall -Wextra -Werror
LDFLAGS:=-L$(LIBDIR) -lpthread -ldl
LDFLAGS:=-L$(LIBDIR) -lpthread -ldl -lrt
# Executables
CC=gcc


+ 48
- 6
communication_techniques/include/batch_queue_common_comm.h View File

@ -1,6 +1,9 @@
#ifndef _BATCH_QUEUE_COMMON_COMM_H_
#define _BATCH_QUEUE_COMMON_COMM_H_ 1
#include <stdint.h>
#include <unistd.h>
/* Non standard include */
#include <commtech.h>
@ -10,27 +13,66 @@
struct channel
{
void * volatile buf[2 * BUF_SIZE / sizeof(void *)] __attribute__ ((aligned (CACHE_LINE_SIZE)));
/* buf must be the first field to allow the buf_mask test */
void * volatile buf[2][BUF_SIZE / sizeof(void *)] __attribute__ ((aligned (CACHE_LINE_SIZE)));
struct channel *mapping1; /* accesses to buf[0] and state */
struct channel *mapping2; /* accesses to buf[1] */
uintptr_t buf_mask;
int unused[20] __attribute__ ((aligned (CACHE_LINE_SIZE)));
volatile unsigned int state:1 __attribute__ ((aligned (CACHE_LINE_SIZE)));
unsigned int sender_idx __attribute__ ((aligned (CACHE_LINE_SIZE)));
unsigned int receiver_idx __attribute__ ((aligned (CACHE_LINE_SIZE)));
void * volatile *sender_ptr __attribute__ ((aligned (CACHE_LINE_SIZE)));
void * volatile *receiver_ptr __attribute__ ((aligned (CACHE_LINE_SIZE)));
};
#ifndef _BATCH_QUEUE_C_
#ifndef PAGE_SIZE_HELPER
#define PAGE_SIZE_HELPER 1
uintptr_t _bq_page_mask;
void *create_comm_channel_internal(void);
static void *create_comm_channel_helper(void) __attribute__ ((unused));
static void *create_comm_channel_helper(void)
{
int ret;
struct channel *channel;
ret = sysconf(_SC_PAGESIZE);
if (ret == -1)
return NULL;
_bq_page_mask = ~(ret - 1);
channel = create_comm_channel_internal();
channel->buf_mask = sizeof channel->buf[0] - 1;
return channel;
}
#else
extern unsigned int _bq_page_mask;
#endif /* PAGE_SIZE_HELPER */
#define create_comm_channel() create_comm_channel_helper()
__BEGIN_DECLS
static inline void send(struct channel *channel, void **addr)
{
channel->buf[channel->sender_idx++] = addr;
channel->sender_idx %= 2 * (BUF_SIZE / sizeof(void *));
if (!(channel->sender_idx % (BUF_SIZE / sizeof(void *))))
uintptr_t sender_ptr_high;
*channel->sender_ptr++ = addr;
if (unlikely(!((uintptr_t) channel->sender_ptr & channel->buf_mask)))
{
while (channel->state);
channel->state = 1;
sender_ptr_high =
(uintptr_t) channel->sender_ptr & _bq_page_mask;
if ((void *) sender_ptr_high == channel->mapping1)
channel->sender_ptr = channel->mapping2->buf[1];
else
channel->sender_ptr = channel->mapping1->buf[0];
}
}
__END_DECLS
#endif /* _BATCH_QUEUE_C_ */
#endif

+ 114
- 29
communication_techniques/src/communication/batch_queue.c View File

@ -1,24 +1,93 @@
#define _BATCH_QUEUE_C_ 1
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdint.h>
#include <limits.h>
/* Non standard include */
#include <commtech.h>
#include <specific_comm.h>
#define BASE_SHM_NAME "/channel"
#define ROUNDUP(size) ((size + page_size) & ~(page_size - 1))
static uintptr_t buf_mask;
static uintptr_t page_mask;
static int nb_buf_entries;
static unsigned int page_size;
void *create_comm_channel(void)
void *create_comm_channel_internal(void)
{
struct channel *channel;
int ret, shm_fd;
static int chan_idx = 0;
char shm_name[NAME_MAX];
struct channel *channel1, *channel2;
if (!posix_memalign((void **) &channel, CACHE_LINE_SIZE, sizeof(struct channel)))
channel1 = NULL;
channel2 = NULL;
ret = sysconf(_SC_PAGESIZE);
if (ret == -1)
{
channel->receiver_idx = 0;
channel->state = 0;
channel->sender_idx = 0;
return channel;
perror("BatchQueue init sysconf");
return NULL;
}
page_size = ret;
page_mask = ~((uintptr_t) (page_size - 1));
ret = snprintf(shm_name, NAME_MAX, BASE_SHM_NAME"%d\n", chan_idx);
if (ret < 0)
{
fprintf(stderr, "BatchQueue init snprintf failed\n");
return NULL;
} else if (ret >= NAME_MAX)
{
fprintf(stderr, "Too many channels created: impossible to ");
fprintf(stderr, "create a channel named "BASE_SHM_NAME);
fprintf(stderr, "%d\n", chan_idx);
return NULL;
}
shm_fd = shm_open(shm_name, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
if (shm_fd == -1)
{
perror("BatchQueue init shm_open failed");
return NULL;
}
ret = ftruncate(shm_fd, sizeof(*channel1));
if (ret == -1)
{
perror("BatchQueue init ftruncate failed");
goto close_file;
}
return NULL;
channel1 = mmap(NULL, ROUNDUP(sizeof(*channel1)),
PROT_READ | PROT_WRITE, MAP_PRIVATE, shm_fd, 0);
channel2 = mmap(NULL, ROUNDUP(sizeof(*channel1)),
PROT_READ | PROT_WRITE, MAP_PRIVATE, shm_fd, 0);
if ((channel1 == MAP_FAILED) || (channel2 == MAP_FAILED))
{
perror("Batchqueue init mmap failed");
channel1 = NULL;
goto close_file;
}
channel1->mapping1 = channel1;
channel1->mapping2 = channel2;
channel1->state = 0;
channel1->sender_ptr = channel1->buf[0];
channel1->receiver_ptr = channel1->buf[0];
buf_mask = sizeof channel1->buf[0] - 1;
nb_buf_entries = sizeof channel1->buf[0] / sizeof channel1->buf[0][0];
close_file:
shm_unlink(shm_name);
return channel1;
}
int end_producer(void *unused __attribute__ ((unused)))
@ -28,8 +97,17 @@ int end_producer(void *unused __attribute__ ((unused)))
int destroy_comm_channel(void *channel)
{
free(channel);
return 0;
size_t mapping_size;
struct channel *mapping1, *mapping2, *channel_ptr;
channel_ptr = (struct channel *) channel;
mapping1 = channel_ptr->mapping1;
mapping2 = channel_ptr->mapping2;
mapping_size = ROUNDUP(sizeof(*mapping1));
if (munmap(mapping1, mapping_size) || munmap(mapping2, mapping_size))
return -1;
else
return 0;
}
/*
@ -44,12 +122,20 @@ void *recv_one_data(struct channel *channel)
{
void *result;
if (unlikely(!(channel->receiver_idx % (BUF_SIZE / sizeof(void *)))))
if (unlikely(!((uintptr_t) channel->receiver_ptr & buf_mask)))
while (!channel->state);
result = channel->buf[channel->receiver_idx++];
channel->receiver_idx %= (2 * BUF_SIZE) / sizeof(void *);
if (unlikely(!(channel->receiver_idx % (BUF_SIZE / sizeof(void *)))))
result = *channel->receiver_ptr++;
if (unlikely(!((uintptr_t) channel->receiver_ptr & buf_mask)))
{
uintptr_t rcvr_ptr_high;
rcvr_ptr_high = (uintptr_t) channel->receiver_ptr & page_mask;
channel->state = 0;
if ((void *) rcvr_ptr_high == channel->mapping1)
channel->receiver_ptr = channel->mapping2->buf[1];
else
channel->receiver_ptr = channel->mapping1->buf[0];
}
return result;
}
@ -69,21 +155,20 @@ ssize_t recv_some_data(struct channel *channel, void **buf, size_t count)
nb_read = 0;
while (channel->state && nb_read < count)
{
int i, n;
/*
* cur->receiver_idx point to the last buffer we have read.
* We go to the next cache line "+ (BUF_SIZE / sizeof(void *))"
* (because the line is full of void * and then if we are after
* the second cache line we correct the pointer to point to the
* first one (this is done by the modulo).
*/
i = channel->receiver_idx;
n = channel->receiver_idx + (BUF_SIZE / sizeof(void *));
channel->receiver_idx = n % ((2 * BUF_SIZE) / sizeof(void *));
for(; i < n; i++)
*buf++ = channel->buf[i];
nb_read += BUF_SIZE / sizeof(void *);
void * volatile *chanbuf_ptr;
uintptr_t rcvr_ptr_high;
chanbuf_ptr = channel->receiver_ptr;
channel->receiver_ptr += nb_buf_entries;
rcvr_ptr_high = (uintptr_t) channel->receiver_ptr & page_mask;
for(; chanbuf_ptr != channel->receiver_ptr; chanbuf_ptr++)
*buf++ = *chanbuf_ptr;
nb_read += nb_buf_entries;
channel->state = 0;
if ((void *) rcvr_ptr_high == channel->mapping1)
channel->receiver_ptr = channel->mapping2->buf[1];
else
channel->receiver_ptr = channel->mapping1->buf[0];
}
return nb_read;
}

+ 2
- 1
communication_techniques/src/main.c View File

@ -465,7 +465,8 @@ static int consumer_data(node_param_t *node_param)
}
}
cons_check_value = init_calc_arg;
for(i = 0; i < nb_bufs_sent; i++) {
for(i = 0; i < nb_bufs_sent; i++)
{
for(j = 0; j < WORDS_PER_LINE; j++)
{
void *data;


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