State-db I/o metrics (#4562)

* add usage mod to sp-state-machine

* State usage tracking finalized.

* fix spaces

* add license preamble

* imporove output

* review suggestions

* update naming

* merge fixes

* Update client/db/src/light.rs

Co-Authored-By: Gavin Wood <gavin@parity.io>

Co-authored-by: Gavin Wood <github@gavwood.com>

substrate/primitives/state-machine/src/backend.rs

@@ -18,11 +18,16 @@
 
 use log::warn;
 use hash_db::Hasher;
-use crate::trie_backend::TrieBackend;
-use crate::trie_backend_essence::TrieBackendStorage;
-use sp_trie::{TrieMut, MemoryDB, trie_types::TrieDBMut};
 use codec::Encode;
+
 use sp_core::storage::{ChildInfo, OwnedChildInfo};
+use sp_trie::{TrieMut, MemoryDB, trie_types::TrieDBMut};
+
+use crate::{
+	trie_backend::TrieBackend,
+	trie_backend_essence::TrieBackendStorage,
+	UsageInfo,
+};
 
 /// A state backend is used to read state data and can have changes committed
 /// to it.
@@ -200,6 +205,14 @@ pub trait Backend<H: Hasher>: std::fmt::Debug {
 		txs.consolidate(parent_txs);
 		(root, txs)
 	}
+
+	/// Query backend usage statistics (i/o, memory)
+	///
+	/// Not all implementations are expected to be able to do this. In the
+	/// case when thay don't, empty statistics is returned.
+	fn usage_info(&self) -> UsageInfo {
+		UsageInfo::empty()
+	}
 }
 
 impl<'a, T: Backend<H>, H: Hasher> Backend<H> for &'a T {
@@ -284,7 +297,11 @@ impl<'a, T: Backend<H>, H: Hasher> Backend<H> for &'a T {
 	fn for_key_values_with_prefix<F: FnMut(&[u8], &[u8])>(&self, prefix: &[u8], f: F) {
 		(*self).for_key_values_with_prefix(prefix, f);
 	}
-}
+
+	fn usage_info(&self) -> UsageInfo {
+		(*self).usage_info()
+	}
+ }
 
 /// Trait that allows consolidate two transactions together.
 pub trait Consolidate {

substrate/primitives/state-machine/src/lib.rs

@@ -40,6 +40,7 @@ mod overlayed_changes;
 mod proving_backend;
 mod trie_backend;
 mod trie_backend_essence;
+mod stats;
 
 pub use sp_trie::{trie_types::{Layout, TrieDBMut}, TrieMut, DBValue, MemoryDB};
 pub use testing::TestExternalities;
@@ -68,6 +69,7 @@ pub use trie_backend_essence::{TrieBackendStorage, Storage};
 pub use trie_backend::TrieBackend;
 pub use error::{Error, ExecutionError};
 pub use in_memory_backend::InMemory as InMemoryBackend;
+pub use stats::{UsageInfo, UsageUnit};
 
 type CallResult<R, E> = Result<NativeOrEncoded<R>, E>;
 

substrate/primitives/state-machine/src/stats.rs

@@ -0,0 +1,62 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Usage statistics for state db
+
+use std::time::{Instant, Duration};
+
+/// Measured count of operations and total bytes.
+#[derive(Clone, Debug, Default)]
+pub struct UsageUnit {
+    /// Number of operations.
+    pub ops: u64,
+    /// Number of bytes.
+    pub bytes: u64,
+}
+
+/// Usage statistics for state backend.
+#[derive(Clone, Debug)]
+pub struct UsageInfo {
+    /// Read statistics (total).
+    pub reads: UsageUnit,
+    /// Write statistics.
+    pub writes: UsageUnit,
+    /// Cache read statistics.
+    pub cache_reads: UsageUnit,
+    /// Memory used.
+    pub memory: usize,
+
+    /// Moment at which current statistics has been started being collected.
+    pub started: Instant,
+    /// Timespan of the statistics.
+    pub span: Duration,
+}
+
+impl UsageInfo {
+    /// Empty statistics.
+    ///
+    /// Means no data was collected.
+    pub fn empty() -> Self {
+        Self {
+            reads: UsageUnit::default(),
+            writes: UsageUnit::default(),
+            cache_reads: UsageUnit::default(),
+            memory: 0,
+            started: Instant::now(),
+            span: Default::default(),
+        }
+    }
+}