Revert "Default to number of physical cores on Intel systems"

This reverts commit 2994ded.

Lowering the thread priority for CPU miners seems to be a generally
better solution.

Author: dmarcuse

Cargo.lock

@@ -29,7 +29,6 @@ itertools = "0.8.2"
 num_cpus = "1.11.1"
 crossbeam = "0.7.3"
 ring = "0.16.11"
-raw-cpuid = "7.0.3"
 
 [target.'cfg(windows)'.dependencies]
 winapi = "0.3.8"

Cargo.toml

@@ -9,8 +9,6 @@ use crossbeam::atomic::AtomicCell;
 use crossbeam::channel::RecvTimeoutError;
 use enumset::{EnumSet, EnumSetType};
 use itertools::Itertools;
-use raw_cpuid::CpuId;
-use std::cmp::max;
 use std::fmt::{self, Display, Formatter};
 use std::num::Wrapping;
 use std::str::FromStr;
@@ -71,9 +69,7 @@ impl Display for KernelType {
 
 #[derive(Debug)]
 pub struct CpuInfo {
-    cores: usize,
     threads: usize,
-    default_miner_threads: usize,
     supported: EnumSet<KernelType>,
 }
 
@@ -82,13 +78,10 @@ impl Display for CpuInfo {
         write!(
             f,
             "CPU:\n\
-            \tCores/threads: {cores}/{threads}\n\
-            \tDefault miner threads: {miner_threads}\n\
+            \tThreads: {threads}\n\
             \tSupported kernels: {supported}\n\
             \tUnsupported kernels: {available}",
-            cores = self.cores,
             threads = self.threads,
-            miner_threads = self.default_miner_threads,
             supported = self.supported.iter().join(", "),
             available = (!self.supported).iter().join(", "),
         )
@@ -109,33 +102,11 @@ fn get_best_kernel() -> KernelType {
     Iterator::max(get_supported_kernels().iter()).unwrap_or_default()
 }
 
-/// Some CPUs seem to really struggle when every thread is in use, to the point
-/// of making the miner entirely unusable. This is particularly prevalent on
-/// Intel CPUs, presumably due to the impact of spectre mitigations on
-/// hyperthreading. Thus, we choose a lower default number of threads on Intel
-/// hardware.
-fn get_best_thread_count() -> usize {
-    let cores = num_cpus::get_physical();
-    let threads = num_cpus::get();
-
-    match CpuId::new().get_vendor_info() {
-        Some(v) if v.as_string().to_lowercase().contains("intel") => max(threads - 2, cores),
-        _ => threads,
-    }
-}
-
 pub fn get_cpu_info() -> CpuInfo {
-    let cores = num_cpus::get_physical();
     let threads = num_cpus::get();
-    let default_miner_threads = get_best_thread_count();
     let supported = get_supported_kernels();
 
-    CpuInfo {
-        cores,
-        threads,
-        default_miner_threads,
-        supported,
-    }
+    CpuInfo { threads, supported }
 }
 
 pub struct CpuMiner {
@@ -152,7 +123,7 @@ impl CpuMiner {
         }: &MinerConfig,
     ) -> CpuMiner {
         CpuMiner {
-            threads: cpu_threads.unwrap_or_else(get_best_thread_count),
+            threads: cpu_threads.unwrap_or_else(num_cpus::get),
             kernel_type: cpu_kernel.unwrap_or_else(get_best_kernel),
         }
     }