On Wed, Feb 07, 2018 at 03:50:36PM +0300, Vladimir Sementsov-Ogievskiy wrote: > Introduce latency histogram statics for block devices. > For each accounted operation type latency region [0, +inf) is > divided into subregions by several points. Then, calculate > hits for each subregion. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> > --- > include/block/accounting.h | 9 +++++ > block/accounting.c | 97 > ++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 106 insertions(+) > > diff --git a/include/block/accounting.h b/include/block/accounting.h > index b833d26d6c..9679020f64 100644 > --- a/include/block/accounting.h > +++ b/include/block/accounting.h > @@ -45,6 +45,12 @@ struct BlockAcctTimedStats { > QSLIST_ENTRY(BlockAcctTimedStats) entries; > }; > > +typedef struct BlockLatencyHistogram { > + int size; > + uint64_t *points; /* @size-1 points here (all points, except 0 and +inf) > */ > + uint64_t *histogram[BLOCK_MAX_IOTYPE]; /* @size elements for each type */
The semantics of these fields is not obvious. Please include a comment with an example or ASCII-art diagram so anyone reading the code understands the purpose of the fields without reading all the code. According to Wikipedia and Mathworld, "intervals" and "bins" are commonly used terms: https://en.wikipedia.org/wiki/Histogram http://mathworld.wolfram.com/Histogram.html I suggest: typedef struct { /* The following histogram is represented like this: * * 5| * * 4| * * 3| * * * 2| * * * * 1| * * * * * +------------------ * 10 50 100 * * BlockLatencyHistogram histogram = { * .nbins = 4, * .intervals = {10, 50, 100}, * .bins = {3, 1, 5, 2}, * }; */ size_t nbins; /* Interval boundaries (there are @nbins - 1 elements) */ uint64_t *intervals; /* Frequency data (there are @nbins elements) */ uint64_t *bins[BLOCK_MAX_IOTYPE]; } BlockLatencyHistogram; > +/* block_latency_histogram_compare_func > + * Compare @key with interval [@el, @el+1), where @el+1 is a next array > element > + * after @el. > + * Return: -1 if @key < @el > + * 0 if @key in [@el, @el+1) > + * +1 if @key >= @el+1 "@el+1" is confusing, usually x+1 means "the value of x plus 1", not "y" (a different variable!). I suggest: /* block_latency_histogram_compare_func: * Compare @key with interval [@it[0], @it[1]). * Return: -1 if @key < @it[0] * 0 if @key in [@it[0], @it[1]) * +1 if @key >= @it[1] */ static int block_latency_histogram_compare_func(const void *key, const void *it) > +int block_latency_histogram_set(BlockAcctStats *stats, uint64List *latency) > +{ > + BlockLatencyHistogram *hist = &stats->latency_histogram; > + uint64List *entry; > + uint64_t *ptr; > + int i; > + uint64_t prev = 0; > + > + hist->size = 1; > + > + for (entry = latency; entry; entry = entry->next) { > + if (entry->value <= prev) { > + return -EINVAL; > + } > + hist->size++; > + prev = entry->value; > + } > + > + hist->points = g_renew(uint64_t, hist->points, hist->size - 1); > + for (entry = latency, ptr = hist->points; entry; > + entry = entry->next, ptr++) > + { > + *ptr = entry->value; > + } > + > + for (i = 0; i < BLOCK_MAX_IOTYPE; i++) { > + hist->histogram[i] = g_renew(uint64_t, hist->histogram[i], > hist->size); > + memset(hist->histogram[i], 0, hist->size * sizeof(uint64_t)); Is there a reason for using g_renew() and then clearing everything? This is more concise: g_free(hist->histogram[i]); hist->histogram[i] = g_new0(uint64_t, hist->size);
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