[PATCH v2] Improve the performance of --num-threads -d 31

Minoru Usui min-usui at ti.jp.nec.com
Wed Feb 24 00:13:30 PST 2016


Hi, Zhou

I have one more comment.
I found unused variables.

> -----Original Message-----
> From: kexec [mailto:kexec-bounces at lists.infradead.org] On Behalf Of Zhou Wenjian
> Sent: Wednesday, February 17, 2016 4:06 PM
> To: kexec at lists.infradead.org
> Subject: [PATCH v2] Improve the performance of --num-threads -d 31
> 
> v2:
>         1. address Minoru Usui's comments about magic number and error message
>         2. fix a bug in cyclic mode caused by optimizing
> 
> v1:
>         1. change page_flag.ready's value to enum
>         2. change the patch description
>         3. cleanup some codes
>         4. fix a bug in cyclic mode
> 
> multi-threads implementation will introduce extra cost when handling
> each page. The origin implementation will also do the extra work for
> filtered pages. So there is a big performance degradation in
> --num-threads -d 31.
> The new implementation won't do the extra work for filtered pages any
> more. So the performance of -d 31 is close to that of serial processing.
> 
> The new implementation is just like the following:
>         * The basic idea is producer producing page and consumer writing page.
>         * Each producer have a page_flag_buf list which is used for storing
>           page's description.
>         * The size of page_flag_buf is little so it won't take too much memory.
>         * And all producers will share a page_data_buf array which is
>           used for storing page's compressed data.
>         * The main thread is the consumer. It will find the next pfn and write
>           it into file.
>         * The next pfn is smallest pfn in all page_flag_buf.
> 
> Signed-off-by: Zhou Wenjian <zhouwj-fnst at cn.fujitsu.com>
> ---
>  makedumpfile.c | 266 ++++++++++++++++++++++++++++++++++++++-------------------
>  makedumpfile.h |  31 ++++---
>  2 files changed, 200 insertions(+), 97 deletions(-)
> 
> diff --git a/makedumpfile.c b/makedumpfile.c
> index fa0b779..31329b5 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -3483,7 +3483,8 @@ initial_for_parallel()
>  	unsigned long page_data_buf_size;
>  	unsigned long limit_size;
>  	int page_data_num;
> -	int i;
> +	struct page_flag *current;
> +	int i, j;
> 
>  	len_buf_out = calculate_len_buf_out(info->page_size);
> 
> @@ -3562,8 +3563,10 @@ initial_for_parallel()
>  		      - MAP_REGION * info->num_threads) * 0.6;
> 
>  	page_data_num = limit_size / page_data_buf_size;
> +	info->num_buffers = 3 * info->num_threads;
> 
> -	info->num_buffers = MIN(NUM_BUFFERS, page_data_num);
> +	info->num_buffers = MAX(info->num_buffers, NUM_BUFFERS);
> +	info->num_buffers = MIN(info->num_buffers, page_data_num);
> 
>  	DEBUG_MSG("Number of struct page_data for produce/consume: %d\n",
>  			info->num_buffers);
> @@ -3588,6 +3591,36 @@ initial_for_parallel()
>  	}
> 
>  	/*
> +	 * initial page_flag for each thread
> +	 */
> +	if ((info->page_flag_buf = malloc(sizeof(void *) * info->num_threads))
> +	    == NULL) {
> +		MSG("Can't allocate memory for page_flag_buf. %s\n",
> +				strerror(errno));
> +		return FALSE;
> +	}
> +	memset(info->page_flag_buf, 0, sizeof(void *) * info->num_threads);
> +
> +	for (i = 0; i < info->num_threads; i++) {
> +		if ((info->page_flag_buf[i] = calloc(1, sizeof(struct page_flag))) == NULL) {
> +			MSG("Can't allocate memory for page_flag. %s\n",
> +				strerror(errno));
> +			return FALSE;
> +		}
> +		current = info->page_flag_buf[i];
> +
> +		for (j = 1; j < NUM_BUFFERS; j++) {
> +			if ((current->next = calloc(1, sizeof(struct page_flag))) == NULL) {
> +				MSG("Can't allocate memory for page_flag. %s\n",
> +					strerror(errno));
> +				return FALSE;
> +			}
> +			current = current->next;
> +		}
> +		current->next = info->page_flag_buf[i];
> +	}
> +
> +	/*
>  	 * initial fd_memory for threads
>  	 */
>  	for (i = 0; i < info->num_threads; i++) {
> @@ -3612,7 +3645,8 @@ initial_for_parallel()
>  void
>  free_for_parallel()
>  {
> -	int i;
> +	int i, j;
> +	struct page_flag *current;
> 
>  	if (info->threads != NULL) {
>  		for (i = 0; i < info->num_threads; i++) {
> @@ -3655,6 +3689,19 @@ free_for_parallel()
>  		free(info->page_data_buf);
>  	}
> 
> +	if (info->page_flag_buf != NULL) {
> +		for (i = 0; i < info->num_threads; i++) {
> +			for (j = 0; j < NUM_BUFFERS; j++) {
> +				if (info->page_flag_buf[i] != NULL) {
> +					current = info->page_flag_buf[i];
> +					info->page_flag_buf[i] = current->next;
> +					free(current);
> +				}
> +			}
> +		}
> +		free(info->page_flag_buf);
> +	}
> +
>  	if (info->parallel_info == NULL)
>  		return;
> 
> @@ -7076,10 +7123,10 @@ kdump_thread_function_cyclic(void *arg) {
>  	void *retval = PTHREAD_FAIL;
>  	struct thread_args *kdump_thread_args = (struct thread_args *)arg;
>  	struct page_data *page_data_buf = kdump_thread_args->page_data_buf;
> +	struct page_flag *page_flag_buf = kdump_thread_args->page_flag_buf;
>  	struct cycle *cycle = kdump_thread_args->cycle;
> -	int page_data_num = kdump_thread_args->page_data_num;
> -	mdf_pfn_t pfn;
> -	int index;
> +	mdf_pfn_t pfn = cycle->start_pfn;
> +	int index = kdump_thread_args->thread_num;
>  	int buf_ready;
>  	int dumpable;
>  	int fd_memory = 0;
> @@ -7125,47 +7172,46 @@ kdump_thread_function_cyclic(void *arg) {
>  						kdump_thread_args->thread_num);
>  	}
> 
> -	while (1) {
> -		/* get next pfn */
> -		pthread_mutex_lock(&info->current_pfn_mutex);
> -		pfn = info->current_pfn;
> -		info->current_pfn++;
> -		pthread_mutex_unlock(&info->current_pfn_mutex);
> +	/*
> +	 * filtered page won't take anything
> +	 * unfiltered zero page will only take a page_flag_buf
> +	 * unfiltered non-zero page will take a page_flag_buf and a page_data_buf
> +	 */
> +	while (pfn < kdump_thread_args->end_pfn) {
> +		buf_ready = FALSE;
> 
> -		if (pfn >= kdump_thread_args->end_pfn)
> -			break;
> +		while (page_data_buf[index].used != FALSE ||
> +				pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> +			index = (index + 1) % info->num_buffers;
> 
> -		index = -1;
> -		buf_ready = FALSE;
> +		page_data_buf[index].used = TRUE;
> 
>  		while (buf_ready == FALSE) {
>  			pthread_testcancel();
> -
> -			index = pfn % page_data_num;
> -
> -			if (pfn - info->consumed_pfn > info->num_buffers)
> -				continue;
> -
> -			if (page_data_buf[index].ready != 0)
> +			if (page_flag_buf->ready == FLAG_READY)
>  				continue;
> 
> -			pthread_mutex_lock(&page_data_buf[index].mutex);
> -
> -			if (page_data_buf[index].ready != 0)
> -				goto unlock;
> +			/* get next pfn */
> +			pthread_mutex_lock(&info->current_pfn_mutex);
> +			pfn = info->current_pfn;
> +			info->current_pfn++;
> +			page_flag_buf->ready = FLAG_FILLING;
> +			pthread_mutex_unlock(&info->current_pfn_mutex);
> 
> -			buf_ready = TRUE;
> +			page_flag_buf->pfn = pfn;
> 
> -			page_data_buf[index].pfn = pfn;
> -			page_data_buf[index].ready = 1;
> +			if (pfn >= kdump_thread_args->end_pfn) {
> +				page_data_buf[index].used = FALSE;
> +				page_flag_buf->ready = FLAG_READY;
> +				break;
> +			}
> 
>  			dumpable = is_dumpable(
>  				info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
>  				pfn,
>  				cycle);
> -			page_data_buf[index].dumpable = dumpable;
>  			if (!dumpable)
> -				goto unlock;
> +				continue;
> 
>  			if (!read_pfn_parallel(fd_memory, pfn, buf,
>  					       &bitmap_memory_parallel,
> @@ -7178,11 +7224,11 @@ kdump_thread_function_cyclic(void *arg) {
> 
>  			if ((info->dump_level & DL_EXCLUDE_ZERO)
>  			    && is_zero_page(buf, info->page_size)) {
> -				page_data_buf[index].zero = TRUE;
> -				goto unlock;
> +				page_flag_buf->zero = TRUE;
> +				goto next;
>  			}
> 
> -			page_data_buf[index].zero = FALSE;
> +			page_flag_buf->zero = FALSE;
> 
>  			/*
>  			 * Compress the page data.
> @@ -7232,12 +7278,16 @@ kdump_thread_function_cyclic(void *arg) {
>  				page_data_buf[index].size  = info->page_size;
>  				memcpy(page_data_buf[index].buf, buf, info->page_size);
>  			}
> -unlock:
> -			pthread_mutex_unlock(&page_data_buf[index].mutex);
> +			page_flag_buf->index = index;
> +			buf_ready = TRUE;
> +next:
> +			page_flag_buf->ready = FLAG_READY;
> +			page_flag_buf = page_flag_buf->next;
> 
>  		}
> -	}
> 
> +		pthread_mutex_unlock(&page_data_buf[index].mutex);
> +	}
>  	retval = NULL;
> 
>  fail:
> @@ -7265,14 +7315,15 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  	struct page_desc pd;
>  	struct timeval tv_start;
>  	struct timeval last, new;
> -	unsigned long long consuming_pfn;
>  	pthread_t **threads = NULL;
>  	struct thread_args *kdump_thread_args = NULL;
>  	void *thread_result;
> -	int page_data_num;
> +	int page_buf_num;
>  	struct page_data *page_data_buf = NULL;
>  	int i;
>  	int index;
> +	int end_count, consuming, check_count;
> +	mdf_pfn_t current_pfn, temp_pfn;
> 
>  	if (info->flag_elf_dumpfile)
>  		return FALSE;
> @@ -7319,16 +7370,11 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  	threads = info->threads;
>  	kdump_thread_args = info->kdump_thread_args;
> 
> -	page_data_num = info->num_buffers;
> +	page_buf_num = info->num_buffers;
>  	page_data_buf = info->page_data_buf;
> 
> -	for (i = 0; i < page_data_num; i++) {
> -		/*
> -		 * producer will use pfn in page_data_buf to decide the
> -		 * consumed pfn
> -		 */
> -		page_data_buf[i].pfn = start_pfn - 1;
> -		page_data_buf[i].ready = 0;
> +	for (i = 0; i < page_buf_num; i++) {
> +		page_data_buf[i].used = FALSE;
>  		res = pthread_mutex_init(&page_data_buf[i].mutex, NULL);
>  		if (res != 0) {
>  			ERRMSG("Can't initialize mutex of page_data_buf. %s\n",
> @@ -7342,8 +7388,9 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  		kdump_thread_args[i].len_buf_out = len_buf_out;
>  		kdump_thread_args[i].start_pfn = start_pfn;
>  		kdump_thread_args[i].end_pfn = end_pfn;
> -		kdump_thread_args[i].page_data_num = page_data_num;
> +		kdump_thread_args[i].page_buf_num = page_buf_num;
>  		kdump_thread_args[i].page_data_buf = page_data_buf;
> +		kdump_thread_args[i].page_flag_buf = info->page_flag_buf[i];
>  		kdump_thread_args[i].cycle = cycle;

Main thread passes to start_pfn and end_pfn, but it also passes cycle.
start_pfn and end_pfn equal to cycle->start_pfn and cycle->end_pfn,
so start_pfn and end_pfn members should be removed.

And also, it passes page_buf_num but it isn't used by producer.

>  		res = pthread_create(threads[i], NULL,
> @@ -7356,55 +7403,101 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  		}
>  	}
> 
> -	consuming_pfn = start_pfn;
> -	index = -1;
> +	end_count = 0;
> +	while (1) {
> +		consuming = 0;
> +		check_count = 0;
> 
> -	gettimeofday(&last, NULL);
> +		/*
> +		 * The basic idea is producer producing page and consumer writing page.
> +		 * Each producer have a page_flag_buf list which is used for storing page's description.
> +		 * The size of page_flag_buf is little so it won't take too much memory.
> +		 * And all producers will share a page_data_buf array which is used for storing page's compressed data.
> +		 * The main thread is the consumer. It will find the next pfn and write it into file.
> +		 * The next pfn is smallest pfn in all page_flag_buf.
> +		 */
> +		gettimeofday(&last, NULL);
> +		while (1) {
> +			current_pfn = end_pfn;
> 
> -	while (consuming_pfn < end_pfn) {
> -		index = consuming_pfn % page_data_num;
> +			/*
> +			 * page_flag_buf is in circular linked list.
> +			 * The array info->page_flag_buf[] records the current page_flag_buf in each thread's
> +			 * page_flag_buf list.
> +			 * consuming is used for recording in which thread the pfn is the smallest.
> +			 * current_pfn is used for recording the value of pfn when checking the pfn.
> +			 */
> +			for (i = 0; i < info->num_threads; i++) {
> +				if (info->page_flag_buf[i]->ready == FLAG_UNUSED)
> +					continue;
> +				temp_pfn = info->page_flag_buf[i]->pfn;
> 
> -		gettimeofday(&new, NULL);
> -		if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> -			ERRMSG("Can't get data of pfn %llx.\n", consuming_pfn);
> -			goto out;
> -		}
> +				/*
> +				 * count how many threads have reached the end.
> +				 */
> +				if (temp_pfn >= end_pfn) {
> +					/*
> +					 * prevent setting FLAG_UNUSED being optimized.
> +					 */
> +					MSG("-");
> 
> -		/*
> -		 * check pfn first without mutex locked to reduce the time
> -		 * trying to lock the mutex
> -		 */
> -		if (page_data_buf[index].pfn != consuming_pfn)
> -			continue;
> +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
> 
> -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> -			continue;
> +					info->current_pfn = end_pfn;
> +					end_count++;
> +					continue;
> +				}
> +
> +				if (current_pfn < temp_pfn)
> +					continue;
> 
> -		/* check whether the found one is ready to be consumed */
> -		if (page_data_buf[index].pfn != consuming_pfn ||
> -		    page_data_buf[index].ready != 1) {
> -			goto unlock;
> +				check_count++;
> +				consuming = i;
> +				current_pfn = temp_pfn;
> +			}
> +
> +			/*
> +			 * If all the threads have reached the end, we will finish writing.
> +			 */
> +			if (end_count >= info->num_threads)
> +				goto finish;
> +
> +			/*
> +			 * Since it has the probabilty that there is no page_flag_buf being ready,
> +			 * we should recheck if it happens.
> +			 */
> +			if (check_count == 0)
> +				continue;
> +
> +			/*
> +			 * If the page_flag_buf is not ready, the pfn recorded may be changed.
> +			 * So we should recheck.
> +			 */
> +			if (info->page_flag_buf[consuming]->ready != FLAG_READY) {
> +				gettimeofday(&new, NULL);
> +				if (new.tv_sec - last.tv_sec > WAIT_TIME) {
> +					ERRMSG("Can't get data of pfn.\n");
> +					goto out;
> +				}
> +				continue;
> +			}
> +
> +			if (current_pfn == info->page_flag_buf[consuming]->pfn)
> +				break;
>  		}
> 
>  		if ((num_dumped % per) == 0)
>  			print_progress(PROGRESS_COPY, num_dumped, info->num_dumpable);
> 
> -		/* next pfn is found, refresh last here */
> -		last = new;
> -		consuming_pfn++;
> -		info->consumed_pfn++;

info->consumed_pfn is no longer used by anywhere, 
so consumed_pfn and consumed_pfn_mutex member should be removed.

---
Thanks,
Minoru Usui

> -		page_data_buf[index].ready = 0;
> -
> -		if (page_data_buf[index].dumpable == FALSE)
> -			goto unlock;
> -
>  		num_dumped++;
> 
> -		if (page_data_buf[index].zero == TRUE) {
> +
> +		if (info->page_flag_buf[consuming]->zero == TRUE) {
>  			if (!write_cache(cd_header, pd_zero, sizeof(page_desc_t)))
>  				goto out;
>  			pfn_zero++;
>  		} else {
> +			index = info->page_flag_buf[consuming]->index;
>  			pd.flags      = page_data_buf[index].flags;
>  			pd.size       = page_data_buf[index].size;
>  			pd.page_flags = 0;
> @@ -7420,12 +7513,12 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
>  			 */
>  			if (!write_cache(cd_page, page_data_buf[index].buf, pd.size))
>  				goto out;
> -
> +			page_data_buf[index].used = FALSE;
>  		}
> -unlock:
> -		pthread_mutex_unlock(&page_data_buf[index].mutex);
> +		info->page_flag_buf[consuming]->ready = FLAG_UNUSED;
> +		info->page_flag_buf[consuming] = info->page_flag_buf[consuming]->next;
>  	}
> -
> +finish:
>  	ret = TRUE;
>  	/*
>  	 * print [100 %]
> @@ -7464,7 +7557,7 @@ out:
>  	}
> 
>  	if (page_data_buf != NULL) {
> -		for (i = 0; i < page_data_num; i++) {
> +		for (i = 0; i < page_buf_num; i++) {
>  			pthread_mutex_destroy(&page_data_buf[i].mutex);
>  		}
>  	}
> @@ -7564,6 +7657,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
>  		num_dumped++;
>  		if (!read_pfn(pfn, buf))
>  			goto out;
> +
>  		filter_data_buffer(buf, pfn_to_paddr(pfn), info->page_size);
> 
>  		/*
> diff --git a/makedumpfile.h b/makedumpfile.h
> index e0b5bbf..8a9a5b2 100644
> --- a/makedumpfile.h
> +++ b/makedumpfile.h
> @@ -977,7 +977,7 @@ typedef unsigned long long int ulonglong;
>  #define PAGE_DATA_NUM	(50)
>  #define WAIT_TIME	(60 * 10)
>  #define PTHREAD_FAIL	((void *)-2)
> -#define NUM_BUFFERS	(50)
> +#define NUM_BUFFERS	(20)
> 
>  struct mmap_cache {
>  	char	*mmap_buf;
> @@ -985,28 +985,36 @@ struct mmap_cache {
>  	off_t   mmap_end_offset;
>  };
> 
> +enum {
> +	FLAG_UNUSED,
> +	FLAG_READY,
> +	FLAG_FILLING
> +};
> +struct page_flag {
> +	mdf_pfn_t pfn;
> +	char zero;
> +	char ready;
> +	short index;
> +	struct page_flag *next;
> +};
> +
>  struct page_data
>  {
> -	mdf_pfn_t pfn;
> -	int dumpable;
> -	int zero;
> -	unsigned int flags;
> +	pthread_mutex_t mutex;
>  	long size;
>  	unsigned char *buf;
> -	pthread_mutex_t mutex;
> -	/*
> -	 * whether the page_data is ready to be consumed
> -	 */
> -	int ready;
> +	int flags;
> +	int used;
>  };
> 
>  struct thread_args {
>  	int thread_num;
>  	unsigned long len_buf_out;
>  	mdf_pfn_t start_pfn, end_pfn;
> -	int page_data_num;
> +	int page_buf_num;
>  	struct cycle *cycle;
>  	struct page_data *page_data_buf;
> +	struct page_flag *page_flag_buf;
>  };
> 
>  /*
> @@ -1295,6 +1303,7 @@ struct DumpInfo {
>  	pthread_t **threads;
>  	struct thread_args *kdump_thread_args;
>  	struct page_data *page_data_buf;
> +	struct page_flag **page_flag_buf;
>  	pthread_rwlock_t usemmap_rwlock;
>  	mdf_pfn_t current_pfn;
>  	pthread_mutex_t current_pfn_mutex;
> --
> 1.8.3.1
> 
> 
> 
> 
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