The MIN, MAX, CLAMP, MINIMUM, and MAXIMUM macros appear
throughout the codebase with many re-definitions. Make
a single copy of each in a common header file, and use
the BSD variants of MINIMUM/MAXIMUM due to conflicts in
the system <sys/param.h> headers.
Reasoning:
- implementation was unsound -- broke down when I added a fairly
basic macro definition expanding to a struct initializer in a *.c
file.
- made it way too easy (e.g. via otherwise totally innocuous git
commands) to end up with timestamps such that it always ran
MakeHeader.py but never used its output, leading to overbuild noise
when running what should be a null 'make'.
- but mostly: it's just an awkward way of dealing with C code.
If no pools are imported (ARC size == 0) or the
ZFS module is not in the kernel (/proc/spl/kstat/zfs/arcstats
does not exist), then the Meter reports "Unavailable".
this way a remount of /proc will not reset starttimes
and we can also see startup times for processes started before the mount
of /proc
also record btime (boot time in seconds since epoch) as Linux semi-global
Adds support for showing columns with linux delay accounting.
This information can be read from the netlink interface, and thus we set up a socket to read from that when initializing the LinuxProcessList (LinuxProcessList_initNetlinkSocket). After that, for each process we call LinuxProcessList_readDelayAcctData, which sends a message thru the socket after setting up a callback to get the answer from the Kernel. That callback sets the process total delay time attribute. We then set the delay percent as the percentage of time process cpu time since last scan.
With the CLAMP macro replacing the combination of MIN and MAX, we will
have at least two advantages:
1. It's more obvious semantically.
2. There are no more mixes of confusing uses like MIN(MAX(a,b),c) and
MAX(MIN(a,b),c) and MIN(a,MAX(b,c)) appearing everywhere. We unify
the 'clamping' with a single macro.
Note that the behavior of this CLAMP macro is different from
the combination `MAX(low,MIN(x,high))`.
* This CLAMP macro expands to two comparisons instead of three from
MAX and MIN combination. In theory, this makes the code slightly
smaller, in case that (low) or (high) or both are computed at
runtime, so that compilers cannot optimize them. (The third
comparison will matter if (low)>(high); see below.)
* CLAMP has a side effect, that if (low)>(high) it will produce weird
results. Unlike MIN & MAX which will force either (low) or (high) to
win. No assertion of ((low)<=(high)) is done in this macro, for now.
This CLAMP macro is implemented like described in glib
<http://developer.gnome.org/glib/stable/glib-Standard-Macros.html>
and does not handle weird uses like CLAMP(a++, low++, high--) .
Nathan Scott