On Fri, Feb 24, 2023 at 3:28 PM Rob Landley <r...@landley.net> wrote: > > On 2/23/23 14:35, enh via Toybox wrote: > > On LP64 systems, address space is effectively free, > > I remember when the ipv6 guys said that back in the 1990's. This is why > wikipedia[citation needed] blocks editing from the entire v6 address space. > > > and the security > > folks have found a variety of ways to use large PROT_NONE regions. For > > example, Android currently spends 3GiB on the CFI shadow and 7GiB > > padding the scudo heap, meaning that even toybox cat has a VmSize around > > 10GiB. This means that the default ps output doesn't line up. > > And this is why resident set size was invented.
oh, yeah, and that's literally the next column in the default Android ps output ... the trouble is, i'm a coward, and i don't feel like removing VSIZE from the default ps output. specifically: i'm assuming that people are parsing this output, and i'll break them if i do this, and the benefit of not confusing people who're actually _looking_ at the numbers is less than the cost of breaking all those scripts. (that is, after all, the very reason why the _Android_ default for toybox ps is different from the "default default"!) > Is there an "RSS if everything actually populated was faulted in" metric? RSS > plus swap space plus nonresident file backed pages? Hmmm... It really gets > down > to "what do we WANT to be measuring here, and why"? > > Sigh. SZ and VSZ are the same SLOT_vsize with different units: > > else if (which==PS_SZ) ll >>= 12; > else if (which==PS_VSZ) ll >>= 10; > > (Which implies the "ps -o help" description of SZ is wrong because that > implies > it's RSS instead of VSZ. Or is the SLOT entry wrong and it SHOULD be > SLOT_rss? I > tested all of this by hand at one point...) > > Not digging into it right now. That said, If RSS _isn't_ the right metric, > then > the next place to look would be /proc/self/smaps_rollup which I believe is > newer > than this code and just... sigh. Did they add any of those new metrics to > /proc/self/stat? No of course they didn't, why would they do that... > > > Arguably this should be a change to the default width (currently 7) of > > the VSZ entry in the "typos" array, but as long as desktop Linux isn't > > using its address space for security mitigations, that seemed like it > > might be too contentious. > > Possibly it argues that the VSZ units should be something other than 1k, but > mostly I think it argues that VSZ has become somewhat meaningless on android? yeah, top doesn't have as much of a problem (beyond raising the question of "why does everything have the same vsize?") because it uses the human-readable "10G" form instead. but if i was brave enough to change ps' units, i'd be brave enough to just remove the not-very-meaningful-on-Android field (that ironically is only shown by default on Android, because it was _very_ meaningful back in the 32-bit days!). > *shrug* Applied, but this is kinda whistling past some design questions... > > Rob _______________________________________________ Toybox mailing list Toybox@lists.landley.net http://lists.landley.net/listinfo.cgi/toybox-landley.net
