There is no sense in storing commonPrefix for blockHeader containing only a single item,
since this only increases blockHeader size without any benefits.
This should improve the performance for items sorting inside inmemoryBlock.MarshalUnsortedData
if they have common prefix.
While at it, improve the performance for inmemoryBlock.updateCommonPrefix for sorted items.
This should improve performance for inmemoryBlock.MarshalSortedData during background merge.
The lifetime of storageBlock is much shorter comparing to the lifetime of inmemoryPart,
so sync.Pool usage should reduce overall memory usage and improve performance
because of better locality of reference when marshaling inmemoryBlock to inmemoryPart.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2247
There is no need to sort the underlying data according to sorted items there.
This should reduce cpu usage when registering new time series in `indexdb`.
Thanks to @ahfuzhang for the suggestion at https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2245
Previously bytesutil.Resize() was copying the original byte slice contents to a newly allocated slice.
This wasted CPU cycles and memory bandwidth in some places, where the original slice contents wasn't needed
after slize resizing. Switch such places to bytesutil.ResizeNoCopy().
Rename the original bytesutil.Resize() function to bytesutil.ResizeWithCopy() for the sake of improved readability.
Additionally, allocate new slice with `make()` instead of `append()`. This guarantees that the capacity of the allocated slice
exactly matches the requested size. The `append()` could return a slice with bigger capacity as an optimization for further `append()` calls.
This could result in excess memory usage when the returned byte slice was cached (for instance, in lib/blockcache).
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2007
CPU and memory profiles show that the pool capacity for inmemoryBlock objects is too small.
This results in the increased load on memory allocation code in Go runtime.
Increase the pool capacity in order to reduce the load on Go runtime.
This should reduce memory usage for the pool on systems with big number of CPU cores.
The sync.Pool maintains per-CPU pools, so the total number of objects in the pool
is proportional to the number of available CPU cores. The channel limits the number
of pooled objects by its own capacity. This means smaller number of pooled objects on average.
The pool for inmemoryBlock struct doesn't give any performance gains in production workloads,
while it may result in excess memory usage for inmemoryBlock structs inside the pool during
background merge of indexdb.
This should improve lookup performance if the same `label=value` pair exists
in big number of time series.
This should also reduce memory usage for mergeset data cache, since `tag->metricIDs` rows
occupy less space than the original `tag->metricID` rows.
