On 04/09/2013 06:05 AM, Joonsoo Kim wrote: > I don't think so. > Yes, lowmem_shrink() return number of (in)active lru pages > when nr_to_scan is 0. And in shrink_slab(), we divide it by lru_pages. > lru_pages can vary where shrink_slab() is called, anyway, perhaps this > logic makes total_scan below 128. > You may benefit from looking at the lowmemory patches in this patchset itself. We modified the shrinker API to separate the count and scan phases. With this, the whole nr_to_scan == 0 disappears and the code gets easier to follow. >> > >> > And, interestingly enough, when the file cache has been pruned down >> > to it's smallest possible size, that's when the shrinker *won't run* >> > because the that's when the total_scan will be smaller than the >> > batch size and hence shrinker won't get called. >> > >> > The shrinker is hacky, abuses the shrinker API, and doesn't appear >> > to do what it is intended to do. You need to fix the shrinker, not >> > use it's brokenness as an excuse to hold up a long overdue shrinker >> > rework. > Agreed. I also think shrinker rework is valuable and I don't want > to become a stopper for this change. But, IMHO, at least, we should > notify users of shrinker API to know how shrinker API behavior changed, Except that the behavior didn't change. > because this is unexpected behavior change when they used this API. > When they used this API, they can assume that it is possible to control > logic with seeks and return value(when nr_to_scan=0), but with this patch, > this assumption is broken. > Jonsoo, you are still missing the point. nr_to_scan=0 has nothing to do with this, or with this patch. nr_to_scan will reach 0 ANYWAY if you shrink all objects you have to shrink, which is a *very* common thing to happen. The only case changed here is where this happen when attempting to shrink a small number of objects that is smaller than the batch size. Also, again, the nr_to_scan=0 checks in the shrinker calls have nothing to do with that. They reflect the situation *BEFORE* the shrinker was called. So how many objects we shrunk afterwards have zero to do with it. This is just the shrinker API using the magic value of 0 to mean : "don't shrink, just tell me how much do you have", vs a positive number meaning "try to shrink as much as nr_to_scan objects". -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
