On Wed, Jan 11, 2012 at 02:33:59PM -0800, Ying Han wrote: > On Tue, Jan 10, 2012 at 4:30 PM, Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > On Tue, Jan 10, 2012 at 03:54:05PM -0800, Ying Han wrote: > >> Thank you for the patch and the stats looks reasonable to me, few > >> questions as below: > >> > >> On Tue, Jan 10, 2012 at 7:02 AM, Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > >> > With the single per-zone LRU gone and global reclaim scanning > >> > individual memcgs, it's straight-forward to collect meaningful and > >> > accurate per-memcg reclaim statistics. > >> > > >> > This adds the following items to memory.stat: > >> > >> Some of the previous discussions including patches have similar stats > >> in memory.vmscan_stat API, which collects all the per-memcg vmscan > >> stats. I would like to understand more why we add into memory.stat > >> instead, and do we have plan to keep extending memory.stat for those > >> vmstat like stats? > > > > I think they were put into an extra file in particular to be able to > > write to this file to reset the statistics. But in my opinion, it's > > trivial to calculate a delta from before and after running a workload, > > so I didn't really like adding kernel code for that. > > > > Did you have another reason for a separate file in mind? > > Another reason I had them in separate file is easier to extend. I > don't know if we have plan to have something like memory.vmstat, or > just keep adding stuff into memory.stat. In general, I wanted to keep > the memory.stat being reasonable size including only the basic > statistics. In my existing vmscan_stat path, i have breakdowns of > reclaim stats into file/anon which will make the memory.stat even > larger. Do you think it's a problem of presentation, where we want to allow admins to figure out the memcg parameters at a glance when looking at memory.stat but be able to debug malfunction by looking at the more extensive vmstat file? > >> > áReclaim activity from kswapd due to the memcg's own limit. áOnly > >> > áapplicable to the root memcg for now since kswapd is only triggered > >> > áby physical limits, but kswapd-style reclaim based on memcg hard > >> > álimits is being developped. > >> > > >> > hierarchy_pgreclaim > >> > hierarchy_pgscan > >> > hierarchy_kswapd_pgreclaim > >> > hierarchy_kswapd_pgscan > >> > >> "pgsteal_hierarchy" > >> "pgsteal_kswapd_hierarchy" > >> .. > >> > >> No strong option on the naming, but try to make it more consistent to > >> existing API. > > > > I swear I tried, but the existing naming is pretty screwed up :( > > > > For example, pgscan_direct_* and pgscan_kswapd_* allow you to compare > > scan rates of direct reclaim vs. kswapd reclaim. To get the total > > number of pages reclaimed, you sum them up. > > > > On the other hand, pgsteal_* does not differentiate between direct > > reclaim and kswapd, so to get direct reclaim numbers, you add up the > > pgsteal_* counters and subtract kswapd_steal (notice the lack of pg?), > > which is in turn not available at zone granularity. > > agree and that always confuses me. I just have scripts that present it as 'Direct page reclaimed' and 'Kswapd page reclaimed' when evaluating data so I don't have to remember anymore :-) But I think the wish for consistency is a bit misguided when we end up with something like pgpgin that means something completely different in memcg than it does on the global level. Likewise, I don't want to use pgsteal_* and pgsteal_kswapd_* because of their similarity to /proc/vmstat while the numbers represent something different. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>