bf3afd5f41
Sometimes it is useful to have a quick histogram to represent a certain
distribution -- for example, when investigating a performance regression
in a hash table due to inadequate hashing.
The appended allows us to easily represent a distribution using Unicode
characters. Further, the data structure keeping track of the distribution
is so simple that obtaining its values for off-line processing is trivial.
Example, taking the last 10 commits to QEMU:
Characters in commit title Count
-----------------------------------
39 1
48 1
53 1
54 2
57 1
61 1
67 1
78 1
80 1
qdist_init(&dist);
qdist_inc(&dist, 39);
[...]
qdist_inc(&dist, 80);
char *str = qdist_pr(&dist, 9, QDIST_PR_LABELS);
// -> [39.0,43.6)▂▂ █▂ ▂ ▄[75.4,80.0]
g_free(str);
char *str = qdist_pr(&dist, 4, QDIST_PR_LABELS);
// -> [39.0,49.2)▁█▁▁[69.8,80.0]
g_free(str);
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1465412133-3029-9-git-send-email-cota@braap.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
64 lines
2 KiB
C
64 lines
2 KiB
C
/*
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* Copyright (C) 2016, Emilio G. Cota <cota@braap.org>
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*
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* License: GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef QEMU_QDIST_H
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#define QEMU_QDIST_H
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#include "qemu/osdep.h"
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#include "qemu-common.h"
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#include "qemu/bitops.h"
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/*
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* Samples with the same 'x value' end up in the same qdist_entry,
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* e.g. inc(0.1) and inc(0.1) end up as {x=0.1, count=2}.
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*
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* Binning happens only at print time, so that we retain the flexibility to
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* choose the binning. This might not be ideal for workloads that do not care
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* much about precision and insert many samples all with different x values;
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* in that case, pre-binning (e.g. entering both 0.115 and 0.097 as 0.1)
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* should be considered.
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*/
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struct qdist_entry {
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double x;
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unsigned long count;
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};
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struct qdist {
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struct qdist_entry *entries;
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size_t n;
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size_t size;
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};
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#define QDIST_PR_BORDER BIT(0)
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#define QDIST_PR_LABELS BIT(1)
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/* the remaining options only work if PR_LABELS is set */
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#define QDIST_PR_NODECIMAL BIT(2)
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#define QDIST_PR_PERCENT BIT(3)
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#define QDIST_PR_100X BIT(4)
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#define QDIST_PR_NOBINRANGE BIT(5)
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void qdist_init(struct qdist *dist);
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void qdist_destroy(struct qdist *dist);
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void qdist_add(struct qdist *dist, double x, long count);
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void qdist_inc(struct qdist *dist, double x);
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double qdist_xmin(const struct qdist *dist);
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double qdist_xmax(const struct qdist *dist);
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double qdist_avg(const struct qdist *dist);
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unsigned long qdist_sample_count(const struct qdist *dist);
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size_t qdist_unique_entries(const struct qdist *dist);
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/* callers must free the returned string with g_free() */
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char *qdist_pr_plain(const struct qdist *dist, size_t n_groups);
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/* callers must free the returned string with g_free() */
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char *qdist_pr(const struct qdist *dist, size_t n_groups, uint32_t opt);
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/* Only qdist code and test code should ever call this function */
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void qdist_bin__internal(struct qdist *to, const struct qdist *from, size_t n);
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#endif /* QEMU_QDIST_H */
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