[LU-14380] Make statahead better support Breadth First Search (BFS) or Depth First Search (DFS)

Related — Sat, 5 Nov 2022 01:02:32 +0000

Batching processing can obtain boost performance.
However, in some file system tree, each level may contain less than 100 entries, but with high depth.
It can do statahead according to Breadth First Search (BFS) or Depth First Search (DFS) access pattern once detect, each time statahead a subtree with more than 1 level, collect enough statahead entries, send the batching RPC via bulk I/O, to improve the tree walking performance.

BFS_Traverse(DIR, Q) {
	Q.enqueue(DIR);
	while |Q| > 0 do
		dir = Q.dequeue()
		opendir(dir);
		while dent = readdir(dir) != NULL do
			stat(dent); process(dent);
			if dent is a directory do
				Q.enqueue(dent);
			end if
		end while
		closedir(dir);
	end while
}
DFS_Traverse(dir) {
	openddir(dir);
	while (dent = readdir(dir) != NULL) do
		if dent is a file then
			stat(dent); process(dent);
		else /* a directory */
			DFS_Traverse(dent)
		end if
	end while
	closedir(dir);
}

Whamcloud Community JIRA

[LU-14380] Make statahead better support Breadth First Search (BFS) or Depth First Search (DFS)