On 12/14/2012 03:37 AM, Michal Hocko wrote: > On Thu 13-12-12 23:50:30, Johannes Weiner wrote: >> On Thu, Dec 13, 2012 at 10:25:43PM +0000, Satoru Moriya wrote: >>> >>> I introduced swappiness check here with fe35004f because, in some >>> cases, we prefer OOM to swap out pages to detect problems as soon as >>> possible. Basically, we design the system not to swap out and so if >>> it causes swapping, something goes wrong. >> >> I might be missing something terribly obvious, but... why do you add >> swap space to the system in the first place? Or in case of cgroups, >> why not set the memsw limit equal to the memory limit? > > I can answer the later. Because memsw comes with its price and > swappiness is much cheaper. On the other hand it makes sense that > swappiness==0 doesn't swap at all. Or do you think we should get back > to _almost_ doesn't swap at all? >
Right. One of the reason is what Michal described above and another reason that I thought is softlimit. softlimit reclaim always works with priority=0. Therefore, if we set softlimit to one memcg without swappiness=0, the kernel scans both anonymous and filebacked pages during soft limit reclaim for the memcg and reclaims them. Regards, Satoru -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
