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top: Change the way the ZFS ARC compression ratio is calculated

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Based on feedback from OpenZFS developers Matt Ahrens and George Wilson,
the calculation of the ratio no longer takes in to account overhead.

The old formula could result in reporting a negative compression ratio

This could confuse the user or give a false impression that there would be
an advantage to disabling the compressed ARC feature.

The new formula will more closely match an average of the on-disk
compression ratio, as reported by the ZFS property 'compressratio'

MFC after:	3 days
Sponsored by:	ScaleEngine Inc.
This commit is contained in:
Allan Jude 2017-06-12 19:51:57 +00:00
parent ff6c17c94e
commit d9a7232865
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=319866
1 changed files with 3 additions and 5 deletions
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8
usr.bin/top/machine.c
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@ -188,9 +188,9 @@ char *arcnames[] = {
NULL
};
int carc_stats[5];
int carc_stats[4];
char *carcnames[] = {
"K Compressed, ", "K Uncompressed, ", ":1 Ratio, ", "K Overhead",
"K Compressed, ", "K Uncompressed, ", ":1 Ratio, ",
NULL
};
@ -580,11 +580,9 @@ get_system_info(struct system_info *si)
if (carc_enabled) {
GETSYSCTL("kstat.zfs.misc.arcstats.compressed_size", arc_stat);
carc_stats[0] = arc_stat >> 10;
carc_stats[2] = arc_stat >> 10; /* For ratio */
GETSYSCTL("kstat.zfs.misc.arcstats.uncompressed_size", arc_stat);
carc_stats[1] = arc_stat >> 10;
carc_stats[2] = arc_stats[0]; /* ARC Total */
GETSYSCTL("kstat.zfs.misc.arcstats.overhead_size", arc_stat);
carc_stats[3] = arc_stat >> 10;
si->carc = carc_stats;
}