On Thu, 11 Feb 2010 13:51:36 -0800 (PST) David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Thu, 11 Feb 2010, Andrew Morton wrote: > > > > Changing any value that may have a tendency to be hardcoded elsewhere is > > > always controversial, but I think the nature of /proc/pid/oom_adj allows > > > us to do so for two specific reasons: > > > > > > - hardcoded values tend not the fall within a range, they tend to either > > > always prefer a certain task for oom kill first or disable oom killing > > > entirely. The current implementation uses this as a bitshift on a > > > seemingly unpredictable and unscientific heuristic that is very > > > difficult to predict at runtime. This means that fewer and fewer > > > applications would hardcode a value of '8', for example, because its > > > semantics depends entirely on RAM capacity of the system to begin with > > > since badness() scores are only useful when used in comparison with > > > other tasks. > > > > You'd be amazed what dumb things applications do. Get thee to > > http://google.com/codesearch?hl=en&lr=&q=[^a-z]oom_adj[^a-z]&sbtn=Search > > and start reading. All 641 matches ;) > > > > Here's one which which writes -16: > > http://google.com/codesearch/p?hl=en#eN5TNOm7KtI/trunk/wlan/vendor/asus/eeepc/init.rc&q=[^a-z]oom_adj[^a-z]&sa=N&cd=70&ct=rc > > > > Let's not change the ABI please. > > > > Sigh, this is going to require the amount of system memory to be > partitioned into OOM_ADJUST_MAX, 15, chunks and that's going to be the > granularity at which we'll be able to either bias or discount memory usage > of individual tasks by: instead of being able to do this with 0.1% > granularity we'll now be limited to 100 / 15, or ~7%. That's ~9GB on my > 128GB system just because this was originally a bitshift. The upside is > that it's now linear and not exponential. Can you add newly-named knobs (rather than modifying the existing ones), deprecate the old ones and then massage writes to the old ones so that they talk into the new framework? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>