[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.
This commit is contained in:
Thomas Preud'homme
parent
fba09b60b8
commit
a20c9a8a21
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@ -14,7 +14,7 @@ COMMDIR:=communication
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# I know -finline-functions and -finline-functions-called-once are enabled by
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# -O3 but I did this in case gcc behaviour change one day
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CFLAGS:=-c -O3 -finline-functions -finline-functions-called-once -Wall -Wextra -Werror
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LDFLAGS:=-L$(LIBDIR) -lpthread -ldl
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LDFLAGS:=-L$(LIBDIR) -lpthread -ldl -lrt
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# Executables
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CC=gcc
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@ -1,6 +1,9 @@
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#ifndef _BATCH_QUEUE_COMMON_COMM_H_
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#define _BATCH_QUEUE_COMMON_COMM_H_ 1
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#include <stdint.h>
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#include <unistd.h>
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/* Non standard include */
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#include <commtech.h>
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@ -10,27 +13,66 @@
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struct channel
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{
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void * volatile buf[2 * BUF_SIZE / sizeof(void *)] __attribute__ ((aligned (CACHE_LINE_SIZE)));
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/* buf must be the first field to allow the buf_mask test */
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void * volatile buf[2][BUF_SIZE / sizeof(void *)] __attribute__ ((aligned (CACHE_LINE_SIZE)));
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struct channel *mapping1; /* accesses to buf[0] and state */
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struct channel *mapping2; /* accesses to buf[1] */
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uintptr_t buf_mask;
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int unused[20] __attribute__ ((aligned (CACHE_LINE_SIZE)));
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volatile unsigned int state:1 __attribute__ ((aligned (CACHE_LINE_SIZE)));
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unsigned int sender_idx __attribute__ ((aligned (CACHE_LINE_SIZE)));
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unsigned int receiver_idx __attribute__ ((aligned (CACHE_LINE_SIZE)));
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void * volatile *sender_ptr __attribute__ ((aligned (CACHE_LINE_SIZE)));
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void * volatile *receiver_ptr __attribute__ ((aligned (CACHE_LINE_SIZE)));
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};
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#ifndef _BATCH_QUEUE_C_
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#ifndef PAGE_SIZE_HELPER
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#define PAGE_SIZE_HELPER 1
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uintptr_t _bq_page_mask;
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void *create_comm_channel_internal(void);
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static void *create_comm_channel_helper(void) __attribute__ ((unused));
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static void *create_comm_channel_helper(void)
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{
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int ret;
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struct channel *channel;
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ret = sysconf(_SC_PAGESIZE);
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if (ret == -1)
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return NULL;
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_bq_page_mask = ~(ret - 1);
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channel = create_comm_channel_internal();
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channel->buf_mask = sizeof channel->buf[0] - 1;
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return channel;
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}
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#else
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extern unsigned int _bq_page_mask;
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#endif /* PAGE_SIZE_HELPER */
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#define create_comm_channel() create_comm_channel_helper()
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__BEGIN_DECLS
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static inline void send(struct channel *channel, void **addr)
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{
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channel->buf[channel->sender_idx++] = addr;
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channel->sender_idx %= 2 * (BUF_SIZE / sizeof(void *));
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if (!(channel->sender_idx % (BUF_SIZE / sizeof(void *))))
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uintptr_t sender_ptr_high;
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*channel->sender_ptr++ = addr;
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if (unlikely(!((uintptr_t) channel->sender_ptr & channel->buf_mask)))
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{
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while (channel->state);
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channel->state = 1;
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sender_ptr_high =
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(uintptr_t) channel->sender_ptr & _bq_page_mask;
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if ((void *) sender_ptr_high == channel->mapping1)
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channel->sender_ptr = channel->mapping2->buf[1];
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else
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channel->sender_ptr = channel->mapping1->buf[0];
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}
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}
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__END_DECLS
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#endif /* _BATCH_QUEUE_C_ */
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#endif
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@ -1,24 +1,93 @@
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#define _BATCH_QUEUE_C_ 1
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#include <stdio.h>
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#include <stdlib.h>
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#include <pthread.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdint.h>
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#include <limits.h>
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/* Non standard include */
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#include <commtech.h>
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#include <specific_comm.h>
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#define BASE_SHM_NAME "/channel"
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#define ROUNDUP(size) ((size + page_size) & ~(page_size - 1))
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void *create_comm_channel(void)
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static uintptr_t buf_mask;
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static uintptr_t page_mask;
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static int nb_buf_entries;
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static unsigned int page_size;
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void *create_comm_channel_internal(void)
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{
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struct channel *channel;
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int ret, shm_fd;
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static int chan_idx = 0;
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char shm_name[NAME_MAX];
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struct channel *channel1, *channel2;
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if (!posix_memalign((void **) &channel, CACHE_LINE_SIZE, sizeof(struct channel)))
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channel1 = NULL;
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channel2 = NULL;
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ret = sysconf(_SC_PAGESIZE);
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if (ret == -1)
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{
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channel->receiver_idx = 0;
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channel->state = 0;
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channel->sender_idx = 0;
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return channel;
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perror("BatchQueue init sysconf");
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return NULL;
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}
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return NULL;
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page_size = ret;
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page_mask = ~((uintptr_t) (page_size - 1));
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ret = snprintf(shm_name, NAME_MAX, BASE_SHM_NAME"%d\n", chan_idx);
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if (ret < 0)
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{
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fprintf(stderr, "BatchQueue init snprintf failed\n");
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return NULL;
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} else if (ret >= NAME_MAX)
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{
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fprintf(stderr, "Too many channels created: impossible to ");
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fprintf(stderr, "create a channel named "BASE_SHM_NAME);
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fprintf(stderr, "%d\n", chan_idx);
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return NULL;
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}
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shm_fd = shm_open(shm_name, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
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if (shm_fd == -1)
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{
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perror("BatchQueue init shm_open failed");
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return NULL;
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}
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ret = ftruncate(shm_fd, sizeof(*channel1));
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if (ret == -1)
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{
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perror("BatchQueue init ftruncate failed");
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goto close_file;
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}
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channel1 = mmap(NULL, ROUNDUP(sizeof(*channel1)),
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PROT_READ | PROT_WRITE, MAP_PRIVATE, shm_fd, 0);
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channel2 = mmap(NULL, ROUNDUP(sizeof(*channel1)),
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PROT_READ | PROT_WRITE, MAP_PRIVATE, shm_fd, 0);
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if ((channel1 == MAP_FAILED) || (channel2 == MAP_FAILED))
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{
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perror("Batchqueue init mmap failed");
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channel1 = NULL;
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goto close_file;
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}
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channel1->mapping1 = channel1;
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channel1->mapping2 = channel2;
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channel1->state = 0;
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channel1->sender_ptr = channel1->buf[0];
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channel1->receiver_ptr = channel1->buf[0];
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buf_mask = sizeof channel1->buf[0] - 1;
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nb_buf_entries = sizeof channel1->buf[0] / sizeof channel1->buf[0][0];
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close_file:
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shm_unlink(shm_name);
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return channel1;
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}
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int end_producer(void *unused __attribute__ ((unused)))
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@ -28,8 +97,17 @@ int end_producer(void *unused __attribute__ ((unused)))
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int destroy_comm_channel(void *channel)
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{
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free(channel);
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return 0;
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size_t mapping_size;
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struct channel *mapping1, *mapping2, *channel_ptr;
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channel_ptr = (struct channel *) channel;
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mapping1 = channel_ptr->mapping1;
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mapping2 = channel_ptr->mapping2;
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mapping_size = ROUNDUP(sizeof(*mapping1));
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if (munmap(mapping1, mapping_size) || munmap(mapping2, mapping_size))
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return -1;
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else
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return 0;
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}
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/*
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@ -44,12 +122,20 @@ void *recv_one_data(struct channel *channel)
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{
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void *result;
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if (unlikely(!(channel->receiver_idx % (BUF_SIZE / sizeof(void *)))))
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if (unlikely(!((uintptr_t) channel->receiver_ptr & buf_mask)))
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while (!channel->state);
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result = channel->buf[channel->receiver_idx++];
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channel->receiver_idx %= (2 * BUF_SIZE) / sizeof(void *);
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if (unlikely(!(channel->receiver_idx % (BUF_SIZE / sizeof(void *)))))
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result = *channel->receiver_ptr++;
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if (unlikely(!((uintptr_t) channel->receiver_ptr & buf_mask)))
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{
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uintptr_t rcvr_ptr_high;
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rcvr_ptr_high = (uintptr_t) channel->receiver_ptr & page_mask;
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channel->state = 0;
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if ((void *) rcvr_ptr_high == channel->mapping1)
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channel->receiver_ptr = channel->mapping2->buf[1];
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else
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channel->receiver_ptr = channel->mapping1->buf[0];
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}
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return result;
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}
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@ -69,21 +155,20 @@ ssize_t recv_some_data(struct channel *channel, void **buf, size_t count)
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nb_read = 0;
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while (channel->state && nb_read < count)
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{
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int i, n;
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/*
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* cur->receiver_idx point to the last buffer we have read.
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* We go to the next cache line "+ (BUF_SIZE / sizeof(void *))"
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* (because the line is full of void * and then if we are after
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* the second cache line we correct the pointer to point to the
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* first one (this is done by the modulo).
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*/
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i = channel->receiver_idx;
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n = channel->receiver_idx + (BUF_SIZE / sizeof(void *));
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channel->receiver_idx = n % ((2 * BUF_SIZE) / sizeof(void *));
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for(; i < n; i++)
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*buf++ = channel->buf[i];
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nb_read += BUF_SIZE / sizeof(void *);
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void * volatile *chanbuf_ptr;
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uintptr_t rcvr_ptr_high;
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chanbuf_ptr = channel->receiver_ptr;
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channel->receiver_ptr += nb_buf_entries;
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rcvr_ptr_high = (uintptr_t) channel->receiver_ptr & page_mask;
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for(; chanbuf_ptr != channel->receiver_ptr; chanbuf_ptr++)
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*buf++ = *chanbuf_ptr;
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nb_read += nb_buf_entries;
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channel->state = 0;
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if ((void *) rcvr_ptr_high == channel->mapping1)
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channel->receiver_ptr = channel->mapping2->buf[1];
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else
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channel->receiver_ptr = channel->mapping1->buf[0];
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}
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return nb_read;
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}
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@ -465,7 +465,8 @@ static int consumer_data(node_param_t *node_param)
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}
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}
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cons_check_value = init_calc_arg;
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for(i = 0; i < nb_bufs_sent; i++) {
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for(i = 0; i < nb_bufs_sent; i++)
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{
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for(j = 0; j < WORDS_PER_LINE; j++)
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{
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void *data;
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