We tried to maximize the bitmap buffer to get the best performance, but the performance degradation caused by multi-cycle processing looks very small according to the benchmark on 2TB memory: https://lkml.org/lkml/2013/3/26/914 This result means we don't need to make an effort to maximize the bitmap buffer, it will just increase the risk of OOM. This patch sets a small fixed value (4MB) as a safety limit, it may be safer and enough in most cases. Signed-off-by: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp> --- makedumpfile.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/makedumpfile.c b/makedumpfile.c index b8f1ec4..c23667b 100644 --- a/makedumpfile.c +++ b/makedumpfile.c @@ -8946,13 +8946,15 @@ out: /* - * Choose the lesser value of the two below as the size of cyclic buffer. - * - the size enough for storing the 1st/2nd bitmap for the whole of vmcore - * - 80% of free memory (as safety limit) + * Choose the lesser value of the three below as the size of cyclic buffer. + * - the size enough for storing the 1st or 2nd bitmap for the whole of vmcore + * - 4MB as sufficient value + * - 60% of free memory as safety limit */ int calculate_cyclic_buffer_size(void) { unsigned long long limit_size, bitmap_size; + const unsigned long long maximum_size = 4 * 1024 * 1024; if (info->max_mapnr <= 0) { ERRMSG("Invalid max_mapnr(%llu).\n", info->max_mapnr); @@ -8960,17 +8962,18 @@ calculate_cyclic_buffer_size(void) { } /* - * We should keep the size of cyclic buffer within 80% of free memory - * for safety. + * At least, we should keep the size of cyclic buffer within 60% of + * free memory for safety. */ - limit_size = get_free_memory_size() * 0.8; + limit_size = get_free_memory_size() * 0.6; bitmap_size = info->max_mapnr / BITPERBYTE; /* if --split was specified cyclic buffer allocated per dump file */ if (info->num_dumpfile > 1) bitmap_size /= info->num_dumpfile; - info->bufsize_cyclic = MIN(limit_size, bitmap_size); + /* 4MB will be enought for performance according to benchmarks. */ + info->bufsize_cyclic = MIN(MIN(limit_size, maximum_size), bitmap_size); return TRUE; } -- 1.9.0
