On 08/21/2013 06:23 PM, Dave Hansen wrote: > On 08/21/2013 08:22 AM, Jerome Marchand wrote: >>>> Instead of introducing yet another tunable, why don't we just make the >>>> ratio that comes in from the user more fine-grained? >>>> >>>> sysctl overcommit_ratio=0.2 >>>> >>>> We change the internal 'sysctl_overcommit_ratio' to store tenths or >>>> hundreths of a percent (or whatever), then parse the input as two >>>> integers. I don't think we need fully correct floating point parsing >>>> and rounding here, so it shouldn't be too much of a chore. It'd >>>> probably end up being less code than you have as it stands. >>>> >> Now that I think about it, that could break user space. Sure write access >> wouldn't be a problem (one can still write a plain integer), but a script >> that reads a fractional value when it expects an integer might not be able >> to cope with it. > > You're right. Something doing FOO=$(cat overcommit_ratio) and then > trying do do arithmetic would just fail loudly. But, it would probably > fail silently if we create another tunable that all of a sudden returns > 0 (when the kernel is not _behaving_ like it is set to 0). > > I'm not sure there's a good way out of this without breakage (or at > least confusing) of _some_ old scripts/programs. Either way has ups and > downs. > > The existing dirty_ratio/bytes stuff just annoys me because I end up > having to check two places whenever I go looking for it. >
Right. Then we could just use some overcommit_fine_ratio internally and overcommit_ratio would show and set a rounded value. I doubt that a script that reads 80% would notice the difference if it is actually 79.5%. We could also use overcommit_kbytes internally, but then overcommit_ratio would fluctuate if RAM ram is added/removed (e.g. memory hotplug or baloon driver). That might be a problem. -- 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/
