From 918644c4e6c9ccdf635a72ee40781a23d4a4d6af Mon Sep 17 00:00:00 2001
From: Maxim <59533214+biryukovmaxim@users.noreply.github.com>
Date: Mon, 2 Oct 2023 14:05:00 +0400
Subject: [PATCH] Add warning for negative IO delta values (#277)

Added a warning message in case the new IO read or write bytes values are less than the previous values. This was done using the unwrap_or_else() function to prevent the program from potentially crashing when the subtraction operation results in a negative value.
---
 metrics/perf_monitor/src/lib.rs | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/metrics/perf_monitor/src/lib.rs b/metrics/perf_monitor/src/lib.rs
index 5a805553d..e7215d71d 100644
--- a/metrics/perf_monitor/src/lib.rs
+++ b/metrics/perf_monitor/src/lib.rs
@@ -4,7 +4,7 @@ use kaspa_core::{
         service::{AsyncService, AsyncServiceFuture},
         tick::{TickReason, TickService},
     },
-    trace,
+    trace, warn,
 };
 use workflow_perf_monitor::{
     cpu::{processor_numbers, ProcessStat},
@@ -48,8 +48,15 @@ impl<TS: AsRef<TickService>> Monitor<TS> {
             let IOStats { read_bytes: disk_io_read_bytes, write_bytes: disk_io_write_bytes, .. } = get_process_io_stats()?;
 
             let time_delta = last_log_time.elapsed();
-            let read_delta = disk_io_read_bytes - last_read;
-            let write_delta = disk_io_write_bytes - last_written;
+
+            let read_delta = disk_io_read_bytes.checked_sub(last_read).unwrap_or_else(|| {
+                warn!("new io read bytes value is less than previous, new: {disk_io_read_bytes}, previous: {last_read}");
+                0
+            });
+            let write_delta = disk_io_write_bytes.checked_sub(last_written).unwrap_or_else(|| {
+                warn!("new io write bytes value is less than previous, new: {disk_io_write_bytes}, previous: {last_written}");
+                0
+            });
 
             let now = Instant::now();
             last_log_time = now;