Jim Warner d16fd8e462 top: snapshot /proc/stat reads to minimize distortions
Almost forever, top has been accessing the /proc/stat/
directory one line at a time until either smp_num_cpus
was reached or (more recently) Screen_rows is reached.

When NUMA/Nodes support is enabled screen rows will no
longer serve as a limit because all cpus must be read.

With this commit, the entire /proc/stat/ directory can
be read at once so all statistics will be frozen. Thus
individual cpus will no longer keep "ticing" until top
gets around to accessing them via some separate fgets.

The distortion this commit eliminates was quite easily
seen when comparing old/new tops using: individual cpu
stats vs. cpu summary; a healthy delay interval of 3-5
seconds; manually synchronized update cycles (the hard
part); some system loading (maybe another top at -d0).

Additionally, this patch eliminates some long standing
unnecessary initialization made possible because of an
allocation via calloc. If some parts are never touched
by sscanf due to a kernel version, it's unnecessary to
repeatedly re-initialize those portions to zero again.

Reference(s):
. numa extensions added
commit 8d989c68c0
. useless initialization evolution (old to new)
commit e54c8239b1
commit 9278134e49
commit fd62123562
commit f348575edc

Signed-off-by: Jim Warner <james.warner@comcast.net>
2013-04-24 08:29:22 +10:00
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2013-04-07 18:31:26 +10:00
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2012-01-13 22:42:38 +01:00
2012-03-04 08:04:24 +11:00
2012-04-16 12:55:53 +02:00
2002-02-01 22:47:29 +00:00
2012-09-27 22:08:04 +10:00
2012-04-16 12:55:53 +02:00
2012-03-03 18:28:52 +11:00
2012-04-16 12:55:53 +02:00
2002-02-01 22:47:29 +00:00
2012-04-16 12:55:53 +02:00
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2012-12-26 23:14:09 +11:00
2012-05-29 22:20:36 +10:00
2012-04-16 12:55:53 +02:00
2013-03-20 16:32:06 +01:00

COMPATIBILITY

    This code is intended for use with Linux 2.6.xx, 3.x and
    hopefully all future kernels.

INSTALLATION

    If you are using git version of the project you need extra step.

    ./autogen.sh

    After that, and everyone using .tar.xz version of procps-ng, can
    do normal build.  Read './configure --help' to select options for
    your needs.

    ./configure
    make
    make install

    If you have DejaGNU installed you can run optional test suite.

    make check

HOW TO CONTRIBUTE

    See Documentation/BUGS file.

PACKAGING

    If you are a downstream maintainer (packager) for a Linux
    distribution, please avoid causing troubles.  This section
    applies to you.

    Avoid maintaining distribution specific patches.  Send your
    patches to upstream, where they are at least reviewed, if not
    included.

    Please forward bug reports. If your bug database is public and
    busy enough to bother with, please make this known.  Follow
    Debian's lead in making the bug database easy to comment on via
    email without need for an account.

    For normal packages, ensure that you do not add debugging flags
    to the CFLAGS variable.

UPSTREAM & BUG REPORTS

    procps-ng <procps@freelists.org>
Description
Command line and full screen utilities for browsing procfs, a "pseudo" file system dynamically generated by Linux to provide information about the status of entries in its process table.
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