[PATCH v1] Improve the performance of --num-threads -d 31

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Hello,

> -----Original Message-----
> From: kexec [mailto:kexec-bounces at lists.infradead.org] On Behalf Of Minoru Usui
> Sent: Thursday, February 04, 2016 8:52 AM
> To: Zhou Wenjian <zhouwj-fnst at cn.fujitsu.com>; kexec at lists.infradead.org
> Subject: Re: [PATCH v1] Improve the performance of --num-threads -d 31
> 
> Hi, Zhou
> 
> I have some comments.
> I'm sorry if I have misunderstood your code.
> 
> > -----Original Message-----
> > From: kexec [mailto:kexec-bounces at lists.infradead.org] On Behalf Of Zhou Wenjian
> > Sent: Monday, February 01, 2016 3:22 PM
> > To: kexec at lists.infradead.org
> > Subject: [PATCH v1] Improve the performance of --num-threads -d 31
> >
> > 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 | 258 ++++++++++++++++++++++++++++++++++++++-------------------
> >  makedumpfile.h |  31 ++++---
> >  2 files changed, 193 insertions(+), 96 deletions(-)
> >
> > diff --git a/makedumpfile.c b/makedumpfile.c
> > index fa0b779..0ecd065 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] = malloc(sizeof(struct page_flag))) == NULL) {
> 
> Fist element of struct page_flag in circular list is allocated by malloc(),
> but other elements are allocated by calloc().(see below)
> I think both elements should be allocated by calloc().
> 
> > +			MSG("Can't allocate memory for page_flag_buf. %s\n",
> > +				strerror(errno));
> > +			return FALSE;
> > +		}
> > +		current = info->page_flag_buf[i];
> > +
> > +		for (j = 1; j < NUM_BUFFERS; j++) {
> > +			if ((current->next = calloc(0, sizeof(struct page_flag))) == NULL) {
> > +				MSG("Can't allocate memory for data of page_data_buf. %s\n",
> > +					strerror(errno));
> > +				return FALSE;
> > +			}
> 
> 
> First argument of calloc() should be 1, not 0.
> And there is typo in error message.
> Allocated element is not page_data_buf.
> 
> > +			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;
> > +	int index = kdump_thread_args->thread_num;
> >  	int buf_ready;
> >  	int dumpable;
> >  	int fd_memory = 0;
> > @@ -7125,47 +7172,47 @@ 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 (page_flag_buf->pfn < kdump_thread_args->end_pfn) {
> 
> At first, page_flag_buf->pfn is not initialized.
> I think this block should be replaced with the following code.
> 
> ===
>   do {
>     :
>   } while(page_flag_buf->pfn < kdump_thread_args->end_pfn)
> ===

I'm sorry, above suggestion is meaningless in terms of page_flag_buf->pfn is uninitialized.
It should be replaced like following.

===
  while (1) {
    :
    while (buf_ready == FALSE) {
       :
      if (pfn >= kdump_thread_args->end_pfn) {
         :
        goto finish;
      }
      :
    }
    :
  }
finish:
===

Thanks,
Minoru Usui

 
> > +		buf_ready = FALSE;
> >
> > -		if (pfn >= kdump_thread_args->end_pfn)
> > -			break;
> > +		while (page_data_buf[index].used != 0 ||
> > +				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 = 1;
> 
> "1" is a magic number.
> It should be changed TRUE or FALSE.
> 
> >  		while (buf_ready == FALSE) {
> >  			pthread_testcancel();
> > -
> > -			index = pfn % page_data_num;
> > -
> > -			if (pfn - info->consumed_pfn > info->num_buffers)
> > +			if (page_flag_buf->ready == FLAG_READY)
> >  				continue;
> 
> At first, page_flag_buf->ready is uninitialized, too.
> Should it be initialized in head part of this function, even if FLAG_UNUSED is defined 0?
> 
> 
> >
> > -			if (page_data_buf[index].ready != 0)
> > -				continue;
> > -
> > -			pthread_mutex_lock(&page_data_buf[index].mutex);
> > +			/* 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);
> >
> > -			if (page_data_buf[index].ready != 0)
> > -				goto unlock;
> > +			page_flag_buf->pfn = pfn;
> 
> It set FLAG_FILLING to page_flag_buf->ready before setting pfn to page_flag_buf->pfn.
> But consumer gets page_flag_buf->pfn after checking page_flag_buf->ready != FLAG_UNUSED
> in getting minimum pfn of each thread block.
> Should it set page_flag_buf->pfn first?
> 
> >
> > -			buf_ready = TRUE;
> > -
> > -			page_data_buf[index].pfn = pfn;
> > -			page_data_buf[index].ready = 1;
> > +			if (pfn >= kdump_thread_args->end_pfn) {
> > +				page_data_buf[index].used = 0;
> > +				page_flag_buf->ready = FLAG_READY;
> > +				info->current_pfn--;
> > +				break;
> > +			}
> 
> This block decrements info->current_pfn without info->current_pfn_mutex.
> I think this block should be moved into previous pthread_mutex_lock(info->current_pfn_mutex) block, so it can remove.
> 
> >
> >  			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 +7225,11 @@ 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;
> >  			}
> 
> First, this code gets page_data_buf, then it gets page_flag_buf.
> However, if processed pfn is zero page,
> it processes next pfn while keeping page_data_buf.
> 
> I think it should get page_flag_buf, then get page_data_buf
> in order to shorten the holding period of the page_data_buf[index].mutex.
> 
> Thanks,
> Minoru Usui
> 
> >
> > -			page_data_buf[index].zero = FALSE;
> > +			page_flag_buf->zero = FALSE;
> >
> >  			/*
> >  			 * Compress the page data.
> > @@ -7232,12 +7279,16 @@ 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 +7316,15 @@ 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 +7371,11 @@ 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 = 0;
> >  		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 +7389,9 @@ 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;
> >
> >  		res = pthread_create(threads[i], NULL,
> > @@ -7356,55 +7404,94 @@ write_kdump_pages_parallel_cyclic(struct cache_data *cd_header,
> >  		}
> >  	}
> >
> > -	consuming_pfn = start_pfn;
> > -	index = -1;
> > +	while (1) {
> > +		consuming = 0;
> > +		check_count = 0;
> > +		end_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.
> > +		 */
> > +		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) {
> > +					end_count++;
> > +					info->page_flag_buf[i]->ready = FLAG_UNUSED;
> > +					continue;
> > +				}
> >
> > -		/*
> > -		 * check pfn first without mutex locked to reduce the time
> > -		 * trying to lock the mutex
> > -		 */
> > -		if (page_data_buf[index].pfn != consuming_pfn)
> > -			continue;
> > +				if (current_pfn < temp_pfn)
> > +					continue;
> >
> > -		if (pthread_mutex_trylock(&page_data_buf[index].mutex) != 0)
> > -			continue;
> > +				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;
> > +
> > +			/*
> > +			 * When we check the pfn in page_flag_buf, it may be being produced.
> > +			 * So we should wait until it is ready to use. And if the pfn is
> > +			 * different from the value when we check, we should rechoose the buf.
> > +			 */
> > +			gettimeofday(&last, NULL);
> > +			while (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;
> > +				}
> > +			}
> >
> > -		/* 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;
> > +			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++;
> > -		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 +7507,12 @@ 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 = 0;
> >  		}
> > -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 +7551,7 @@ 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 +7651,7 @@ 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
> >
> >
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> 
> _______________________________________________
> kexec mailing list
> kexec at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec



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