Method mmapHeadChunks

tsdb/head.go:1972–1996

mmapHeadChunks iterates all memSeries stored on Head ready for m-mapping and calls mmapChunks() on each of them. There are two types of chunks that store samples for each memSeries: A) Head chunk - stored on Go heap, when new samples are appended they go there. B) M-mapped chunks - memory mapped ch

()

// M-mapping is serialised via the per-series lock and done away from the sample append path,
// since holding the lock during an append could delay the next scrape or cause query timeouts.
func (h *Head) mmapHeadChunks() {
	var count int
	for i := range h.series.size {
		if h.series.mmapReady[i].Load() == 0 {
			continue // No series in this stripe need mmapping.
		}

		h.series.locks[i].RLock()
		for _, series := range h.series.series[i] {
			if series.headChunkCount.Load() < 2 { // < 2 means 0 or 1 head chunks, nothing to mmap.
				continue
			}

			series.Lock()
			n := series.mmapChunks(h.chunkDiskMapper)
			series.Unlock()
			if n > 0 {
				count += n
				h.series.decMmapReady(series.ref)
			}
		}
		h.series.locks[i].RUnlock()
	}
	h.metrics.mmapChunksTotal.Add(float64(count))
}

// seriesHashmap lets TSDB find a memSeries by its label set, via a 64-bit hash.
// There is one map for the common case where the hash value is unique, and a