This patch adds a started counter, that is used to mark the number of
operation that were started.
This counter serves two purposes, it is a better indication for when to
sample the data and it is used to indicate how many pending operations
are.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
This patch contains two changes to the histogram implementation. It uses
a simpler method to calculate the estimated mean (simply divide the
estimated sum with the number of samples) and to make sure that there
will always be values in the histogram, it start with taking a sample
(when there are no samples) and then use the mask to decide if to sample
or not.
Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
The histogrm object is used both as a general counter for the number of
events and for statistics and sampling.
This chanage the histogram implementation, so it would support spares
sampling while keeping the total number of event accurate.
The implementation includes the following:
Remove the template nature of the histogram, as it is used only for
timer and use the name ihistogram instead.
If in the future we'll need a histogram for other types, we can use the
histogrma name for it.
a total counter was added that count the number of events that are part
of the statistic calculation.
A helper methods where added to the ihistogram to handle the latency
counter object.
According to the sample mask it would mark the latency object as start
if the counter and the mask are non zero and it would accept the latency
object in its mark method, in which if the latency was not start, it
will not be added and only the 'count' counter that counts the total
number of events will be incremented.
This should reduce the impact of latency calculation to a neglectable
effect.
Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
The histogram object is equivalent to the Histogram used in Origin. It
collect multiple values about the data:
Count, Min, Max, Sum, variance and the sum of square that are used for
std calculation.
It also contain a sample of the last n elements, that are stored in a
circular buffer.
The histogram is used by the API to report histogram statistics.
As the API does not support unsigned integer, the count is signed.
Typically the base type of the histogram is int64_t, so ihistogram was
defined as such.
Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
