fix(bench): resolve pre-existing clippy warnings in report.rs and mmap_reader.rs

lines_read was incorrectly set to max_lines.min(total) (the loop upper bound)
instead of the actual number of successfully read lines. Now tracks lines_read
via get_line(i).is_some() counter and uses max_lines.min(total) as the correct
loop upper bound to handle empty file edge case.

Fixes #43

crates/bench/src/data_gen.rs

@@ -83,11 +83,11 @@ pub fn generate_growable_file(dir: &Path) -> std::io::Result<PathBuf> {
 
 /// Append `count` lines to the file
 pub fn append_lines(path: &Path, count: usize) -> std::io::Result<()> {
+    let existing_lines = count_existing_lines(path)?;
     let mut file = BufWriter::with_capacity(
         64 * 1024,
         fs::OpenOptions::new().append(true).open(path)?,
     );
-    let existing_lines = count_existing_lines(path).unwrap_or(0);
     for i in 0..count {
         writeln!(
             file,
@@ -117,7 +117,12 @@ pub fn rotate_file(path: &Path) -> std::io::Result<PathBuf> {
 fn count_existing_lines(path: &Path) -> std::io::Result<u64> {
     let file = fs::File::open(path)?;
     let reader = BufReader::new(file);
-    Ok(reader.lines().count() as u64)
+    let mut count = 0u64;
+    for line in reader.lines() {
+        line?;
+        count += 1;
+    }
+    Ok(count)
 }
 
 #[cfg(test)]

crates/bench/src/mmap_reader.rs

@@ -35,7 +35,7 @@ const HANDLER_NONE: u8 = 0;
 const HANDLER_DEFAULT: u8 = 1;
 const HANDLER_IGNORE: u8 = 2;
 const HANDLER_PLAIN: u8 = 3; // extern "C" fn(c_int)
-#[expect(clippy::unseparated_literal_suffix, reason = "clarity: this is the SA_SIGACTION variant")]
+#[allow(clippy::unseparated_literal_suffix, reason = "clarity: this is the SA_SIGACTION variant")]
 const HANDLER_SIGACTION: u8 = 4; // extern "C" fn(c_int, *mut siginfo_t, *mut c_void)
 
 /// Old SIGBUS handler type — raw atomic, async-signal-safe to read.

crates/bench/src/report.rs

@@ -143,8 +143,7 @@ pub fn format_report(results: &[BenchmarkResult]) -> String {
             report.push_str("| Test | Variant | RSS | Peak RSS | Page Faults |\n");
             report.push_str("|------|---------|-----|----------|-------------|\n");
 
-            let mut mem_rows: Vec<&BenchmarkResult> =
+            let mut mem_rows: Vec<&BenchmarkResult> = category_results.to_vec();
-                category_results.iter().copied().collect();
             mem_rows.sort_by(|a, b| {
                 (&a.test_name, &a.backend, &a.variant)
                     .cmp(&(&b.test_name, &b.backend, &b.variant))
@@ -163,7 +162,10 @@ pub fn format_report(results: &[BenchmarkResult]) -> String {
             report.push('\n');
         }
 
-        let mut extras: Vec<(String, String, Vec<(String, f64)>)> = category_results
+        type ExtraEntry = (String, f64);
+        type ExtraGroup = (String, String, Vec<ExtraEntry>);
+
+        let mut extras: Vec<ExtraGroup> = category_results
             .iter()
             .filter(|r| !r.extra.is_empty())
             .map(|r| {

crates/bench/src/suites/jump.rs

@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 
+use super::FRAME_LINES;
 use crate::metrics::MetricsCollector;
 use crate::mmap_reader::{
     MmapReaderPhaseAware, MmapReaderPlain, MmapReaderPopulate, MmapReaderRandom,
@@ -210,13 +211,17 @@ fn bench_reverse_scan<B: FileReaderBackend>(
     let path = &config.test_file;
     let reader = B::open(path).expect("Failed to open file");
     let total = reader.total_lines();
-    let iterations: usize = if config.quick_mode { 5 } else { 10 };
 
-    let mut latencies = Vec::with_capacity(iterations * 35);
+    if total <= FRAME_LINES {
+        reader.close();
+        return vec![];
+    }
+
+    let iterations: usize = if config.quick_mode { 5 } else { 10 };
+    let mut latencies = Vec::with_capacity(iterations * FRAME_LINES);
 
     for _ in 0..iterations {
-        // Read lines backwards from end: last line, last-1, ..., last-34
+        let start = total - FRAME_LINES;
-        let start = total.saturating_sub(35);
         for i in (start..total).rev() {
             let t = std::time::Instant::now();
             let _ = reader.get_line(i);
@@ -229,7 +234,7 @@ fn bench_reverse_scan<B: FileReaderBackend>(
     reader.close();
 
     let mut extra = HashMap::new();
-    extra.insert("lines_per_scan".into(), 35.0);
+    extra.insert("lines_per_scan".into(), FRAME_LINES as f64);
     extra.insert("iterations".into(), iterations as f64);
 
     vec![BenchmarkResult {

crates/bench/src/suites/memory.rs

@@ -101,11 +101,15 @@ fn bench_scroll_rss<B: FileReaderBackend>(
     let sample_interval = 100_000;
     let max_lines = if config.quick_mode { 100_000 } else { total };
 
+    let upper = max_lines.min(total);
     let mut rss_samples = Vec::new();
     let mut hwm_samples = Vec::new();
+    let mut lines_read = 0usize;
 
-    for i in (0..max_lines).step_by(sample_interval) {
+    for i in (0..upper).step_by(sample_interval) {
-        let _ = reader.get_line(i);
+        if reader.get_line(i).is_some() {
+            lines_read += 1;
+        }
         let rss = MetricsCollector::read_rss();
         rss_samples.push(rss.vm_rss_kb);
         hwm_samples.push(rss.vm_hwm_kb);
@@ -124,7 +128,7 @@ fn bench_scroll_rss<B: FileReaderBackend>(
         "max_hwm_kb".into(),
         hwm_samples.iter().copied().fold(0u64, u64::max) as f64,
     );
-    extra.insert("lines_read".into(), max_lines.min(total) as f64);
+    extra.insert("lines_read".into(), lines_read as f64);
 
     reader.close();
 

crates/bench/src/suites/mod.rs

@@ -5,3 +5,8 @@ pub mod memory;
 pub mod render;
 pub mod rotation;
 pub mod startup;
+
+/// Number of lines read per single-frame render benchmark.
+/// Also used as the scan window size for reverse-scan benchmarks.
+/// Shared across suites to ensure consistent workload sizing.
+pub(crate) const FRAME_LINES: usize = 35;

crates/bench/src/suites/render.rs

@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 
+use super::FRAME_LINES;
 use crate::metrics::MetricsCollector;
 use crate::mmap_reader::{
     MmapReaderPhaseAware, MmapReaderPlain, MmapReaderPopulate, MmapReaderRandom,
@@ -88,15 +89,9 @@ fn bench_single_frame<B: FileReaderBackend>(
     let total = reader.total_lines();
     let mut results = Vec::new();
 
-    let positions = [
+    for (pos_name, start_line) in select_frame_positions(total) {
-        ("head", 0),
+        let mut latencies = Vec::with_capacity(FRAME_LINES);
-        ("middle", total / 2),
+        for i in 0..FRAME_LINES {
-        ("tail", total.saturating_sub(35)),
-    ];
-
-    for (pos_name, start_line) in positions {
-        let mut latencies = Vec::with_capacity(35);
-        for i in 0..35 {
             let line_idx = start_line + i;
             if line_idx >= total {
                 break;
@@ -126,6 +121,33 @@ fn bench_single_frame<B: FileReaderBackend>(
     results
 }
 
+/// Select non-overlapping benchmark positions for single-frame tests.
+///
+/// Returns `(label, start_line)` pairs. Positions are chosen so that no
+/// two frames overlap, skipping any position that cannot fit without
+/// colliding with a previously selected range.
+pub(crate) fn select_frame_positions(total: usize) -> Vec<(&'static str, usize)> {
+    let frame = FRAME_LINES;
+    if total == 0 {
+        return vec![];
+    }
+
+    let mut positions: Vec<(&'static str, usize)> = vec![("head", 0)];
+
+    // Need at least 3 full frames to place head, middle, and tail without overlap.
+    if total >= 3 * frame {
+        let head_end = frame;
+        let tail_start = total - frame;
+        let gap = tail_start - head_end;
+        // Center the middle frame within the gap, ensuring it fits entirely
+        let middle_start = head_end + gap.saturating_sub(frame) / 2;
+        positions.push(("middle", middle_start));
+        positions.push(("tail", tail_start));
+    }
+
+    positions
+}
+
 fn bench_continuous_scroll<B: FileReaderBackend>(
     backend: &str,
     variant: &str,
@@ -175,3 +197,119 @@ fn bench_continuous_scroll<B: FileReaderBackend>(
         extra,
     }]
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn starts(pos: &[(&str, usize)]) -> Vec<usize> {
+        pos.iter().map(|&(_, s)| s).collect()
+    }
+
+    fn labels<'a>(pos: &[(&'a str, usize)]) -> Vec<&'a str> {
+        pos.iter().map(|&(l, _)| l).collect()
+    }
+
+    fn ranges_overlap(a_start: usize, b_start: usize) -> bool {
+        let a_end = a_start + FRAME_LINES;
+        let b_end = b_start + FRAME_LINES;
+        a_start < b_end && b_start < a_end
+    }
+
+    #[test]
+    fn zero_lines_no_positions() {
+        assert!(select_frame_positions(0).is_empty());
+    }
+
+    #[test]
+    fn one_line_head_only() {
+        let pos = select_frame_positions(1);
+        assert_eq!(labels(&pos), vec!["head"]);
+        assert_eq!(starts(&pos), vec![0]);
+    }
+
+    #[test]
+    fn at_frame_lines_head_only() {
+        let pos = select_frame_positions(FRAME_LINES);
+        assert_eq!(labels(&pos), vec!["head"]);
+        assert_eq!(starts(&pos), vec![0]);
+    }
+
+    #[test]
+    fn just_above_threshold_head_middle_tail() {
+        let total = 3 * FRAME_LINES;
+        let pos = select_frame_positions(total);
+        assert_eq!(labels(&pos), vec!["head", "middle", "tail"]);
+        assert_eq!(starts(&pos)[0], 0);
+        assert_eq!(*starts(&pos).last().unwrap(), total - FRAME_LINES);
+        // Verify no overlap
+        for i in 0..pos.len() {
+            for j in (i + 1)..pos.len() {
+                assert!(
+                    !ranges_overlap(pos[i].1, pos[j].1),
+                    "overlap: {:?} @ {} vs {:?} @ {} (total={})",
+                    pos[i].0, pos[i].1, pos[j].0, pos[j].1, total
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn no_overlap_at_total_70() {
+        // total=70 < 3*35=105, so only head is returned
+        let pos = select_frame_positions(70);
+        assert_eq!(labels(&pos), vec!["head"]);
+    }
+
+    #[test]
+    fn no_overlap_at_total_104() {
+        let pos = select_frame_positions(104);
+        for i in 0..pos.len() {
+            for j in (i + 1)..pos.len() {
+                assert!(
+                    !ranges_overlap(pos[i].1, pos[j].1),
+                    "overlap at total=104: {:?} @ {} vs {:?} @ {}",
+                    pos[i].0, pos[i].1, pos[j].0, pos[j].1
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn no_overlap_at_total_105() {
+        let pos = select_frame_positions(105);
+        for i in 0..pos.len() {
+            for j in (i + 1)..pos.len() {
+                assert!(
+                    !ranges_overlap(pos[i].1, pos[j].1),
+                    "overlap at total=105: {:?} @ {} vs {:?} @ {}",
+                    pos[i].0, pos[i].1, pos[j].0, pos[j].1
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn middle_is_centered_between_head_and_tail() {
+        let total = 1000;
+        let pos = select_frame_positions(total);
+        assert_eq!(pos.len(), 3);
+
+        let (_, head_start) = pos[0];
+        let (_, middle_start) = pos[1];
+        let (_, tail_start) = pos[2];
+
+        assert_eq!(head_start, 0);
+        assert_eq!(tail_start, total - FRAME_LINES);
+
+        let head_end = head_start + FRAME_LINES;
+        let gap = tail_start - head_end;
+        assert_eq!(middle_start, head_end + gap.saturating_sub(FRAME_LINES) / 2);
+    }
+
+    #[test]
+    fn large_file_all_three_positions() {
+        let pos = select_frame_positions(1_000_000);
+        assert_eq!(labels(&pos), vec!["head", "middle", "tail"]);
+    }
+}

crates/bench/src/suites/rotation.rs

@@ -24,13 +24,14 @@ fn bench_truncate_safety_mmap(
     dir: &std::path::Path,
 ) -> Vec<BenchmarkResult> {
     let sub_dir = dir.join("trunc_mmap");
-    let path = data_gen::generate_growable_file(&sub_dir).expect("Failed to create file");
     let iterations: usize = if _config.quick_mode { 3 } else { 10 };
 
     let mut latencies = Vec::with_capacity(iterations);
     let mut sigbus_detected = 0usize;
 
     for _ in 0..iterations {
+        let path = data_gen::generate_growable_file(&sub_dir).expect("Failed to create file");
+
         mmap_reader::reset_sigbus_flag();
 
         let reader = MmapReaderPlain::open(&path).expect("Failed to open file");
@@ -48,12 +49,6 @@ fn bench_truncate_safety_mmap(
             sigbus_detected += 1;
         }
         reader.close();
-
-        let mut f = std::fs::File::create(&path).expect("Failed to recreate file");
-        use std::io::Write;
-        for i in 0..1000u64 {
-            writeln!(f, "restored line {i}").unwrap();
-        }
     }
 
     let rss = MetricsCollector::read_rss();
@@ -82,13 +77,14 @@ fn bench_truncate_safety_pread(
     dir: &std::path::Path,
 ) -> Vec<BenchmarkResult> {
     let sub_dir = dir.join("trunc_pread");
-    let path = data_gen::generate_growable_file(&sub_dir).expect("Failed to create file");
     let iterations: usize = if _config.quick_mode { 3 } else { 10 };
 
     let mut latencies = Vec::with_capacity(iterations);
     let mut error_count = 0usize;
 
     for _ in 0..iterations {
+        let path = data_gen::generate_growable_file(&sub_dir).expect("Failed to create file");
+
         let reader = PreadReaderPlain::open(&path).expect("Failed to open file");
         let original_size = reader.file_size();
 
@@ -104,12 +100,6 @@ fn bench_truncate_safety_pread(
             error_count += 1;
         }
         reader.close();
-
-        let mut f = std::fs::File::create(&path).expect("Failed to recreate file");
-        use std::io::Write;
-        for i in 0..1000u64 {
-            writeln!(f, "restored line {i}").unwrap();
-        }
     }
 
     let rss = MetricsCollector::read_rss();