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fix histogram median calculation (#263)
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The histogram approximate median is calculated as about double what it
should be.  When we are on the bucket that goes past the median, the
histogram is the *previous* bucket, plus part of this bucket.

Signed-off-by: Matthew Ahrens <[email protected]>
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@ahrens
ahrens authored Mar 9, 2021
1 parent 6630f3b commit db1b967
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Showing 9 changed files with 59 additions and 59 deletions.
2 changes: 1 addition & 1 deletion sdb/commands/zfs/histograms.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,7 @@ def histogram_median(hist: drgn.Object, offset: int = 0) -> int:
for (bucket, value) in enumerate(hist):
space_in_bucket = int(value) << (bucket + offset)
if space_left <= space_in_bucket:
median = 1 << (bucket + offset)
median = 1 << (bucket + offset - 1)
#
# Size of segments may vary within one bucket thus we
# attempt to approximate the median by looking at the
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4 changes: 2 additions & 2 deletions tests/integration/data/regression_output/zfs/spa -H
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 15 ***************
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa089413b8000 meta-domain
seg-size count
-------- -----
Expand All @@ -45,6 +45,6 @@ ADDR NAME
32.0MB: 0
64.0MB: 1 *
128.0MB: 4 ****
Approx. Median: 184.0MB
Approx. Median: 92.0MB
0xffffa08955c44000 rpool
** No histogram data available **
48 changes: 24 additions & 24 deletions tests/integration/data/regression_output/zfs/spa -mH
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 15 ***************
Approx. Median: 384.0MB
Approx. Median: 192.0MB
ADDR STATE AUX DESCRIPTION
------------------------------------------------------------
0xffffa089486fc000 HEALTHY NONE root
Expand All @@ -50,7 +50,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 15 ***************
Approx. Median: 384.0MB
Approx. Median: 192.0MB
ADDR ID OFFSET FREE FRAG UCMU
-----------------------------------------------------------------
0xffffa0894e6e1000 0 0x0 511MB 0% 8KB
Expand All @@ -76,7 +76,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e6e4000 1 0x20000000 511MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -100,7 +100,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e6e2800 2 0x40000000 511MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -124,7 +124,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e6e3800 3 0x60000000 511MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -148,7 +148,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e6e3000 4 0x80000000 511MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -172,7 +172,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e6e4800 5 0xa0000000 511MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -196,7 +196,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e6e7800 6 0xc0000000 511MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -220,7 +220,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e6e2000 7 0xe0000000 511MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -244,7 +244,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e637800 8 0x100000000 511MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -268,7 +268,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e634800 9 0x120000000 511MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -291,7 +291,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e633000 10 0x140000000 511MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -314,7 +314,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e633800 11 0x160000000 509MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -338,7 +338,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e632800 12 0x180000000 511MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -362,7 +362,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e634000 13 0x1a0000000 511MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -386,7 +386,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa0894e631000 14 0x1c0000000 511MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -410,7 +410,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 1 *
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa08948af8000 HEALTHY NONE /dev/sdb1
0xffffa08949ff8000 HEALTHY NONE /dev/sdc1
0xffffa08949e58000 HEALTHY NONE /dev/sdd1
Expand Down Expand Up @@ -453,7 +453,7 @@ ADDR NAME
32.0MB: 0
64.0MB: 1 *
128.0MB: 4 ****
Approx. Median: 184.0MB
Approx. Median: 92.0MB
ADDR STATE AUX DESCRIPTION
------------------------------------------------------------
0xffffa08953aa4000 HEALTHY NONE root
Expand All @@ -478,7 +478,7 @@ ADDR NAME
32.0MB: 0
64.0MB: 1 *
128.0MB: 4 ****
Approx. Median: 184.0MB
Approx. Median: 92.0MB
ADDR ID OFFSET FREE FRAG UCMU
-----------------------------------------------------------------
0xffffa0894c701000 0 0x0 256MB 0% 0B
Expand All @@ -502,7 +502,7 @@ ADDR NAME
16.0MB: 0
32.0MB: 0
64.0MB: 1 *
Approx. Median: 95.9MB
Approx. Median: 48.0MB
0xffffa0894c700800 2 0x20000000 255MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -524,7 +524,7 @@ ADDR NAME
32.0MB: 0
64.0MB: 0
128.0MB: 1 *
Approx. Median: 191.9MB
Approx. Median: 96.0MB
0xffffa0894c706000 3 0x30000000 255MB 0% 8KB
seg-size count
-------- -----
Expand All @@ -546,7 +546,7 @@ ADDR NAME
32.0MB: 0
64.0MB: 0
128.0MB: 1 *
Approx. Median: 192.0MB
Approx. Median: 96.0MB
0xffffa0894c707000 4 0x40000000 223MB 0% 4KB
seg-size count
-------- -----
Expand All @@ -568,12 +568,12 @@ ADDR NAME
32.0MB: 0
64.0MB: 0
128.0MB: 1 *
Approx. Median: 192.0MB
Approx. Median: 96.0MB
0xffffa0894c706800 5 0x50000000 255MB 0% 4KB
seg-size count
-------- -----
128.0MB: 1 *
Approx. Median: 192.0MB
Approx. Median: 96.0MB
0xffffa0894c703000 6 0x60000000 256MB 0% 0B
0xffffa0894c703800 7 0x70000000 256MB 0% 0B
0xffffa0894c705000 8 0x80000000 256MB 0% 0B
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8 changes: 4 additions & 4 deletions tests/integration/data/regression_output/zfs/spa -vH
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 15 ***************
Approx. Median: 384.0MB
Approx. Median: 192.0MB
ADDR STATE AUX DESCRIPTION
------------------------------------------------------------
0xffffa089486fc000 HEALTHY NONE root
Expand All @@ -50,7 +50,7 @@ ADDR NAME
64.0MB: 0
128.0MB: 0
256.0MB: 15 ***************
Approx. Median: 384.0MB
Approx. Median: 192.0MB
0xffffa08948af8000 HEALTHY NONE /dev/sdb1
0xffffa08949ff8000 HEALTHY NONE /dev/sdc1
0xffffa08949e58000 HEALTHY NONE /dev/sdd1
Expand All @@ -76,7 +76,7 @@ ADDR NAME
32.0MB: 0
64.0MB: 1 *
128.0MB: 4 ****
Approx. Median: 184.0MB
Approx. Median: 92.0MB
ADDR STATE AUX DESCRIPTION
------------------------------------------------------------
0xffffa08953aa4000 HEALTHY NONE root
Expand All @@ -101,7 +101,7 @@ ADDR NAME
32.0MB: 0
64.0MB: 1 *
128.0MB: 4 ****
Approx. Median: 184.0MB
Approx. Median: 92.0MB
0xffffa08953aac000 HEALTHY NONE /tmp/dks0
0xffffa08953ab0000 HEALTHY NONE /tmp/dks1
0xffffa08953ab4000 HEALTHY NONE /tmp/dks2
Expand Down
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