On Sun, Mar 06 2016 at 4:39am -0500, Steven Wilton <swilton@xxxxxxxxxxxxxxx> wrote: > I realised that I over-thought the original logic. The attached > patch is much simpler - write back dirty cache entries at the > migration threshold rate when we are over the low watermark, and we > write back as fast as possible when we go over the high watermark. > > The current behaviour can be replicated by setting the high > watermark to 100, and the low watermark to 0. > > regards > > Steven ... > diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c > index 7dab682..7b8b4a3 100644 > --- a/drivers/md/dm-cache-target.c > +++ b/drivers/md/dm-cache-target.c > @@ -2332,6 +2364,8 @@ static void set_cache_size(struct cache *cache, dm_cblock_t size) > } > > #define DEFAULT_MIGRATION_THRESHOLD 2048 > +#define DEFAULT_WRITEBACK_HIGH_WATERMARK 40 > +#define DEFAULT_WRITEBACK_LOW_WATERMARK 30 > These should default to current behavior (100 and 0 respectively, like you mentioned above). This change needs an accompanying Documentation update. It also needs a proper path header to accurately convey the scope of the change. Please post v4 with these changes and then I'll take a closer look (as I'm sure Joe will). But please be aware that in general we want less knobs, not more. Thanks, Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
