On Fri, Mar 03, 2017 at 02:03:31PM +1100, Neil Brown wrote: > On Fri, Feb 17 2017, Shaohua Li wrote: > > > Bump the flush stripe batch size to 2048. For my 12 disks raid > > array, the stripes takes: > > 12 * 4k * 2048 = 96MB > > > > This is still quite small. A hardware raid card generally has 1GB size, > > which we suggest the raid5-cache has similar cache size. > > > > The advantage of a big batch size is we can dispatch a lot of IO in the > > same time, then we can do some scheduling to make better IO pattern. > > > > Last patch prioritizes stripes, so we don't worry about a big flush > > stripe batch will starve normal stripes. > > > > Signed-off-by: Shaohua Li <shli@xxxxxx> > > --- > > drivers/md/raid5-cache.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c > > index 3f307be..b25512c 100644 > > --- a/drivers/md/raid5-cache.c > > +++ b/drivers/md/raid5-cache.c > > @@ -43,7 +43,7 @@ > > /* wake up reclaim thread periodically */ > > #define R5C_RECLAIM_WAKEUP_INTERVAL (30 * HZ) > > /* start flush with these full stripes */ > > -#define R5C_FULL_STRIPE_FLUSH_BATCH 256 > > +#define R5C_FULL_STRIPE_FLUSH_BATCH 2048 > > Fixed numbers are warning signs... I wonder if there is something better > we could do? "conf->max_nr_stripes / 4" maybe? We use that sort of > number elsewhere. > Would that make sense? The code where we check the batch size (in r5c_do_reclaim) already a check: total_cached > conf->min_nr_stripes * 1 / 2 so I think that's ok, no? Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
