Use os.sched_getaffinity to get info about available CPUs

when running inside containers with CPU limits python's
multiprocessing.cpu_count() will return total number of CPU's
available on the machine. However in reality the process and its
children will not be able to be scheduled on all CPUs.
This issue is most pronounced with taskset/cpuset is set for the process.
Causing scheduling contention over limited number of CPU's.

In case of CFS cpu limits, its similar, but due to bursty nature, at least
in a short timeframe the processes will be able to be scheduled on all CPUs.

There is no straightforward way to read the CPU shares assigned via CFS.
So just handling simple case when affinity is explicitly set should be a good start

chia/consensus/blockchain.py

@@ -1,7 +1,6 @@
 import asyncio
 import dataclasses
 import logging
-import multiprocessing
 from concurrent.futures.process import ProcessPoolExecutor
 from enum import Enum
 from typing import Dict, List, Optional, Set, Tuple, Union
@@ -35,6 +34,8 @@
 from chia.util.generator_tools import get_block_header, tx_removals_and_additions
 from chia.util.ints import uint16, uint32, uint64, uint128
 from chia.util.streamable import recurse_jsonify
+from chia.util.cpus import get_available_cpus
+
 
 log = logging.getLogger(__name__)
 
@@ -98,9 +99,8 @@ async def create(
         self = Blockchain()
         self.lock = asyncio.Lock()  # External lock handled by full node
         self.compact_proof_lock = asyncio.Lock()
-        cpu_count = multiprocessing.cpu_count()
-        if cpu_count > 61:
-            cpu_count = 61  # Windows Server 2016 has an issue https://bugs.python.org/issue26903
+        cpu_count = get_available_cpus()
+
         num_workers = max(cpu_count - 2, 1)
         self.pool = ProcessPoolExecutor(max_workers=num_workers)
         log.info(f"Started {num_workers} processes for block validation")

chia/util/cpus.py

@@ -0,0 +1,16 @@
+import os
+import multiprocessing
+
+
+def get_available_cpus() -> int:
+    try:
+        cpu_count = os.sched_getaffinity(0)
+    except AttributeError:
+        cpu_count = multiprocessing.cpu_count()
+
+    # Note: Windows Server 2016 has an issue https://bugs.python.org/issue26903
+    if os.name == "nt":
+        MAX = 61
+        cpu_count = min(cpu_count, MAX)
+
+    return cpu_count

chia/wallet/wallet_blockchain.py

@@ -1,7 +1,6 @@
 import asyncio
 import dataclasses
 import logging
-import multiprocessing
 from concurrent.futures.process import ProcessPoolExecutor
 from enum import Enum
 from typing import Any, Callable, Dict, List, Optional, Set, Tuple
@@ -21,6 +20,7 @@
 from chia.util.errors import Err, ValidationError
 from chia.util.ints import uint32, uint64
 from chia.util.streamable import recurse_jsonify
+from chia.util.cpus import get_available_cpus
 from chia.wallet.block_record import HeaderBlockRecord
 from chia.wallet.wallet_block_store import WalletBlockStore
 from chia.wallet.wallet_coin_store import WalletCoinStore
@@ -95,9 +95,8 @@ async def create(
         self.lock = asyncio.Lock()
         self.coin_store = coin_store
         self.tx_store = tx_store
-        cpu_count = multiprocessing.cpu_count()
-        if cpu_count > 61:
-            cpu_count = 61  # Windows Server 2016 has an issue https://bugs.python.org/issue26903
+        cpu_count = get_available_cpus()
+
         num_workers = max(cpu_count - 2, 1)
         self.pool = ProcessPoolExecutor(max_workers=num_workers)
         log.info(f"Started {num_workers} processes for block validation")