On Mon, Sep 19, 2016 at 5:27 PM, Robert Foss <robert.foss@xxxxxxxxxxxxx> wrote: > > > On 2016-09-19 03:32 PM, Michal Hocko wrote: >> >> On Mon 19-09-16 11:16:31, Robert Foss wrote: >>> >>> On 2016-09-14 05:12 AM, Michal Hocko wrote: >>>> >>>> On Tue 13-09-16 13:27:39, Sonny Rao wrote: >> >> [...] >>>>> >>>>> Given that smaps >>>>> doesn't provide this in a straightforward way, what do you think is >>>>> the right way to provide this information? >>>> >>>> >>>> I would be tempted to sneak it into /proc/<pid>/statm because that looks >>>> like a proper place but getting this information is not for free >>>> performance wise so I am not really sure something that relies on this >>>> file would see unexpected stalls. Maybe this could be worked around by >>>> some caching... I would suggest to check who is actually using this file >>>> (top/ps etc...) >>> >>> >>> What would this caching look like? Can any information be re-used between >>> vma walks? >> >> >> yes basically return the same value if called within HZ or something >> similar. But that assumes that statm latency really matters and it is >> called often enough. > > > Any single application querying more often than HZ, would presumably do so > for accuracy reasons. > However for multiple applications that combined query more often than HZ, > this would most definitely be halpful in terms of performance. > > @Sonny, does chromiumos fall into the first or second category? It's a single application -- and it definitely doesn't query at HZ -- especially given how long it takes to gather the data :-) -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
