On 06/10/14 at 04:54am, Atsushi Kumagai wrote: > 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. ~~~~~ typo, it should be less. > + * - 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. */ ~~~~~~~~ There's a typo, here should be enough. > + info->bufsize_cyclic = MIN(MIN(limit_size, maximum_size), bitmap_size); > > return TRUE; > } > -- > 1.9.0 > > _______________________________________________ > kexec mailing list > kexec at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec
