On Fri, 24.01.14 12:32, Peter Zijlstra (peterz@xxxxxxxxxxxxx) wrote: > > The process starttime is useful for a variety of things, like figuring > > out creation ordering of processes. Or it is useful to detect PID > > reuses in a somewhat reliable way. > > OK, maybe. Changelog should have said so. > > > It is useful information to show the admin in "ps". > > Does the one jiffy rounding really matter there? I doubt it, ps > typically shows in second granularity. Well, it's just annoying. Much of userspace uses CLOCK_MONOTONIC throughout all the local timestamping needs these days, however the jiffy rounding and the fact that "starttime" is based on CLOCK_BOOTTIME makes it hard to compare process timestamps currently with other timestamps... > > Profilers like "bootchart" can use this information to > > plot when precisely specific process got started. From the outside it is > > often useful to see for how long a specific process has already been > > running, for accounting needs, and so on. > > Profilers have far better interfaces than /proc to get information > from. That is true, but note that at least on Fedora taskstats and thing are actually disabled these days in the kernel, since they slow things down too much. The /proc interface is certainly much nicer there, since it relies on a the timestamping the kernel does anyway... > > Note that Dan's patch doesn't add any new timestamp logic to the kernel, > > it just exposes the existing timestamps in a way to userspace that is > > more in line with the rest of timestamps exposed. > > Yeah, Dan was also too lazy to explain the need, and had like 3 typoes > in the inadequate changelog he had. > > He also fails to explain why he needs the timestamp twice, as do you for > that matter. Well, I am mostly interesting int the monotonic timestamp. But given that the kernel keeps the boottime clock value as well, and already exposes it in a skewed way to userspace it looked like a natural choice to also expose that time in a clean way, while we are it... Lennart -- Lennart Poettering, Red Hat -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
