Hello Usui, On 02/23/2016 09:32 AM, Minoru Usui wrote: > Hello, Zhou > > Thank you for reflecting my comments. > I have other comments. > > See below. > >> -----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; >> >> 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("-"); > > Why does this line need? > Please clarify why FLAG_UNUSED is optimized. > I tried but still can't figure out the reason or get better solution. I will be so happy if you can help me. In gdb, I run it by step. The code "info->page_flag_buf[i]->ready = FLAG_UNUSED;" can never be reached. If a breakpoint is set here, the code will never be skipped. >> >> - /* >> - * 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; > > This part doesn't get info->current_pfn_mutex. > It becomes bigger than end_pfn at the end of producer thread in following case. > > === > producer Consumer > --------------------------------------------------------- > pthread_mutex_lock() > pfn = info->current_pfn > info->current_pfn = end_pfn > info->current_pfn++ > -> end_pfn + 1 > pthread_mutex_unlock() > === > > But I know, if this race is happened, processing other producer thread and consumer thread works well > in current cycle. > Because each thread checks whether info->current_pfn >= end_pfn. > > On the other hand, info->current_pfn is initialized to cycle->start_pfn before pthread_create() > in write_kdump_pages_parallel_cyclic(). > This means it does not cause a problem in next cycle, too. > > In other words, my point is following. > > a) When info->current_pfn changes, you have to get info->current_pfn_mutex. > b) If you allow info->current_pfn is bigger than end_pfn at the end of each cycle, > "info->current_pfn = end_pfn;" is unnecessary. > > Honestly, I don't like approach b). You're right. Some thing I thought is wrong. But I don't like lock if I have other choice. I will set info->current_pfn before returning. How about it? -- Thanks Zhou > > Thanks, > Minoru Usui > >> + 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++; >> - 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 >> >> >> >> >> _______________________________________________ >> kexec mailing list >> kexec at lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/kexec
