Merge pull request #2246 from miDeb/sort-automatic-extsort

sort: automatically fall back to extsort

src/uu/sort/BENCHMARKING.md

@@ -72,7 +72,8 @@ Run `cargo build --release` before benchmarking after you make a change!
 ## External sorting
 
 Try running commands with the `-S` option set to an amount of memory to be used, such as `1M`. Additionally, you could try sorting
-huge files (ideally multiple Gigabytes) with `-S`. Creating such a large file can be achieved by running `cat shuffled_wordlist.txt | sort -R >> shuffled_wordlist.txt`
+huge files (ideally multiple Gigabytes) with `-S` (or without `-S` to benchmark with our default value).
+Creating such a large file can be achieved by running `cat shuffled_wordlist.txt | sort -R >> shuffled_wordlist.txt`
 multiple times (this will add the contents of `shuffled_wordlist.txt` to itself).
 Example: Run `hyperfine './target/release/coreutils sort shuffled_wordlist.txt -S 1M' 'sort shuffled_wordlist.txt -S 1M'`
 

src/uu/sort/src/check.rs

@@ -87,6 +87,7 @@ fn reader(
         chunks::read(
             &mut sender,
             recycled_buffer,
+            None,
             &mut carry_over,
             &mut file,
             &mut iter::empty(),

src/uu/sort/src/chunks.rs

@@ -52,13 +52,20 @@ impl Chunk {
 
 /// Read a chunk, parse lines and send them.
 ///
-/// No empty chunk will be sent.
+/// No empty chunk will be sent. If we reach the end of the input, sender_option
+/// is set to None. If this function however does not set sender_option to None,
+/// it is not guaranteed that there is still input left: If the input fits _exactly_
+/// into a buffer, we will only notice that there's nothing more to read at the next
+/// invocation.
 ///
 /// # Arguments
 ///
-/// * `sender_option`: The sender to send the lines to the sorter. If `None`, does nothing.
+/// (see also `read_to_chunk` for a more detailed documentation)
+///
+/// * `sender_option`: The sender to send the lines to the sorter. If `None`, this function does nothing.
 /// * `buffer`: The recycled buffer. All contents will be overwritten, but it must already be filled.
 ///   (i.e. `buffer.len()` should be equal to `buffer.capacity()`)
+/// * `max_buffer_size`: How big `buffer` can be.
 /// * `carry_over`: The bytes that must be carried over in between invocations.
 /// * `file`: The current file.
 /// * `next_files`: What `file` should be updated to next.
@@ -69,6 +76,7 @@ impl Chunk {
 pub fn read(
     sender_option: &mut Option<SyncSender<Chunk>>,
     mut buffer: Vec<u8>,
+    max_buffer_size: Option<usize>,
     carry_over: &mut Vec<u8>,
     file: &mut Box<dyn Read + Send>,
     next_files: &mut impl Iterator<Item = Box<dyn Read + Send>>,
@@ -82,8 +90,14 @@ pub fn read(
             buffer.resize(carry_over.len() + 10 * 1024, 0);
         }
         buffer[..carry_over.len()].copy_from_slice(&carry_over);
-        let (read, should_continue) =
+        let (read, should_continue) = read_to_buffer(
-            read_to_buffer(file, next_files, &mut buffer, carry_over.len(), separator);
+            file,
+            next_files,
+            &mut buffer,
+            max_buffer_size,
+            carry_over.len(),
+            separator,
+        );
         carry_over.clear();
         carry_over.extend_from_slice(&buffer[read..]);
 
@@ -138,7 +152,8 @@ fn parse_lines<'a>(
 /// * `next_files`: When `file` reaches EOF, it is updated to `next_files.next()` if that is `Some`,
 ///    and this function continues reading.
 /// * `buffer`: The buffer that is filled with bytes. Its contents will mostly be overwritten (see `start_offset`
-///   as well). It will not be grown by default, unless that is necessary to read at least two lines.
+///   as well). It will be grown up to `max_buffer_size` if necessary, but it will always grow to read at least two lines.
+/// * `max_buffer_size`: Grow the buffer to at most this length. If None, the buffer will not grow, unless needed to read at least two lines.
 /// * `start_offset`: The amount of bytes at the start of `buffer` that were carried over
 ///    from the previous read and should not be overwritten.
 /// * `separator`: The byte that separates lines.
@@ -153,6 +168,7 @@ fn read_to_buffer(
     file: &mut Box<dyn Read + Send>,
     next_files: &mut impl Iterator<Item = Box<dyn Read + Send>>,
     buffer: &mut Vec<u8>,
+    max_buffer_size: Option<usize>,
     start_offset: usize,
     separator: u8,
 ) -> (usize, bool) {
@@ -162,6 +178,19 @@ fn read_to_buffer(
             Ok(0) => {
                 if read_target.is_empty() {
                     // chunk is full
+                    if let Some(max_buffer_size) = max_buffer_size {
+                        if max_buffer_size > buffer.len() {
+                            // we can grow the buffer
+                            let prev_len = buffer.len();
+                            if buffer.len() < max_buffer_size / 2 {
+                                buffer.resize(buffer.len() * 2, 0);
+                            } else {
+                                buffer.resize(max_buffer_size, 0);
+                            }
+                            read_target = &mut buffer[prev_len..];
+                            continue;
+                        }
+                    }
                     let mut sep_iter = memchr_iter(separator, &buffer).rev();
                     let last_line_end = sep_iter.next();
                     if sep_iter.next().is_some() {

src/uu/sort/src/ext_sort.rs

@@ -5,12 +5,13 @@
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
 
-//! Sort big files by using files for storing intermediate chunks.
+//! Sort big files by using auxiliary files for storing intermediate chunks.
 //!
 //! Files are read into chunks of memory which are then sorted individually and
 //! written to temporary files. There are two threads: One sorter, and one reader/writer.
 //! The buffers for the individual chunks are recycled. There are two buffers.
 
+use std::cmp::Ordering;
 use std::io::{BufWriter, Write};
 use std::path::Path;
 use std::{
@@ -20,30 +21,19 @@ use std::{
     thread,
 };
 
+use itertools::Itertools;
+
 use tempdir::TempDir;
 
 use crate::{
     chunks::{self, Chunk},
-    merge::{self, FileMerger},
+    compare_by, merge, output_sorted_lines, sort_by, GlobalSettings,
-    sort_by, GlobalSettings,
 };
 
-/// Iterator that wraps the
+const MIN_BUFFER_SIZE: usize = 8_000;
-pub struct ExtSortedMerger<'a> {
-    pub file_merger: FileMerger<'a>,
-    // Keep _tmp_dir around, as it is deleted when dropped.
-    _tmp_dir: TempDir,
-}
 
-/// Sort big files by using files for storing intermediate chunks.
+/// Sort files by using auxiliary files for storing intermediate chunks (if needed), and output the result.
-///
+pub fn ext_sort(files: &mut impl Iterator<Item = Box<dyn Read + Send>>, settings: &GlobalSettings) {
-/// # Returns
-///
-/// An iterator that merges intermediate files back together.
-pub fn ext_sort<'a>(
-    files: &mut impl Iterator<Item = Box<dyn Read + Send>>,
-    settings: &'a GlobalSettings,
-) -> ExtSortedMerger<'a> {
     let tmp_dir = crash_if_err!(1, TempDir::new_in(&settings.tmp_dir, "uutils_sort"));
     let (sorted_sender, sorted_receiver) = std::sync::mpsc::sync_channel(1);
     let (recycled_sender, recycled_receiver) = std::sync::mpsc::sync_channel(1);
@@ -51,7 +41,7 @@ pub fn ext_sort<'a>(
         let settings = settings.clone();
         move || sorter(recycled_receiver, sorted_sender, settings)
     });
-    let chunks_read = reader_writer(
+    let read_result = reader_writer(
         files,
         &tmp_dir,
         if settings.zero_terminated {
@@ -66,13 +56,29 @@ pub fn ext_sort<'a>(
         sorted_receiver,
         recycled_sender,
     );
-    let files = (0..chunks_read)
+    match read_result {
+        ReadResult::WroteChunksToFile { chunks_written } => {
+            let files = (0..chunks_written)
                 .map(|chunk_num| tmp_dir.path().join(chunk_num.to_string()))
                 .collect::<Vec<_>>();
-
+            let mut merger = merge::merge(&files, settings);
-    ExtSortedMerger {
+            merger.write_all(settings);
-        file_merger: merge::merge(&files, settings),
+        }
-        _tmp_dir: tmp_dir,
+        ReadResult::SortedSingleChunk(chunk) => {
+            output_sorted_lines(chunk.borrow_lines().iter(), settings);
+        }
+        ReadResult::SortedTwoChunks([a, b]) => {
+            let merged_iter = a
+                .borrow_lines()
+                .iter()
+                .merge_by(b.borrow_lines().iter(), |line_a, line_b| {
+                    compare_by(line_a, line_b, settings) != Ordering::Greater
+                });
+            output_sorted_lines(merged_iter, settings);
+        }
+        ReadResult::EmptyInput => {
+            // don't output anything
+        }
     }
 }
 
@@ -84,6 +90,21 @@ fn sorter(receiver: Receiver<Chunk>, sender: SyncSender<Chunk>, settings: Global
     }
 }
 
+/// Describes how we read the chunks from the input.
+enum ReadResult {
+    /// The input was empty. Nothing was read.
+    EmptyInput,
+    /// The input fits into a single Chunk, which was kept in memory.
+    SortedSingleChunk(Chunk),
+    /// The input fits into two chunks, which were kept in memory.
+    SortedTwoChunks([Chunk; 2]),
+    /// The input was read into multiple chunks, which were written to auxiliary files.
+    WroteChunksToFile {
+        /// The number of chunks written to auxiliary files.
+        chunks_written: usize,
+    },
+}
+
 /// The function that is executed on the reader/writer thread.
 ///
 /// # Returns
@@ -96,7 +117,7 @@ fn reader_writer(
     settings: GlobalSettings,
     receiver: Receiver<Chunk>,
     sender: SyncSender<Chunk>,
-) -> usize {
+) -> ReadResult {
     let mut sender_option = Some(sender);
 
     let mut file = files.next().unwrap();
@@ -106,21 +127,40 @@ fn reader_writer(
     for _ in 0..2 {
         chunks::read(
             &mut sender_option,
-            vec![0; buffer_size],
+            vec![0; MIN_BUFFER_SIZE],
+            Some(buffer_size),
             &mut carry_over,
             &mut file,
             &mut files,
             separator,
             Vec::new(),
             &settings,
-        )
+        );
+        if sender_option.is_none() {
+            // We have already read the whole input. Since we are in our first two reads,
+            // this means that we can fit the whole input into memory. Bypass writing below and
+            // handle this case in a more straightforward way.
+            return if let Ok(first_chunk) = receiver.recv() {
+                if let Ok(second_chunk) = receiver.recv() {
+                    ReadResult::SortedTwoChunks([first_chunk, second_chunk])
+                } else {
+                    ReadResult::SortedSingleChunk(first_chunk)
+                }
+            } else {
+                ReadResult::EmptyInput
+            };
+        }
     }
 
     let mut file_number = 0;
     loop {
         let mut chunk = match receiver.recv() {
             Ok(it) => it,
-            _ => return file_number,
+            _ => {
+                return ReadResult::WroteChunksToFile {
+                    chunks_written: file_number,
+                }
+            }
         };
 
         write(
@@ -129,13 +169,14 @@ fn reader_writer(
             separator,
         );
 
-        let (recycled_lines, recycled_buffer) = chunk.recycle();
-
         file_number += 1;
 
+        let (recycled_lines, recycled_buffer) = chunk.recycle();
+
         chunks::read(
             &mut sender_option,
             recycled_buffer,
+            None,
             &mut carry_over,
             &mut file,
             &mut files,

src/uu/sort/src/merge.rs

@@ -108,6 +108,7 @@ fn reader(
         chunks::read(
             sender,
             recycled_buffer,
+            None,
             carry_over,
             file,
             &mut iter::empty(),

src/uu/sort/src/sort.rs

@@ -93,7 +93,10 @@ static THOUSANDS_SEP: char = ',';
 static NEGATIVE: char = '-';
 static POSITIVE: char = '+';
 
-static DEFAULT_BUF_SIZE: usize = std::usize::MAX;
+// Choosing a higher buffer size does not result in performance improvements
+// (at least not on my machine). TODO: In the future, we should also take the amount of
+// available memory into consideration, instead of relying on this constant only.
+static DEFAULT_BUF_SIZE: usize = 1_000_000_000; // 1 GB
 
 #[derive(Eq, Ord, PartialEq, PartialOrd, Clone, Copy)]
 enum SortMode {
@@ -127,28 +130,35 @@ pub struct GlobalSettings {
     zero_terminated: bool,
     buffer_size: usize,
     tmp_dir: PathBuf,
-    ext_sort: bool,
 }
 
 impl GlobalSettings {
-    // It's back to do conversions for command line opts!
+    /// Interpret this `&str` as a number with an optional trailing si unit.
-    // Probably want to do through numstrcmp somehow now?
+    ///
-    fn human_numeric_convert(a: &str) -> usize {
+    /// If there is no trailing si unit, the implicit unit is K.
-        let num_str = &a[get_leading_gen(a)];
+    /// The suffix B causes the number to be interpreted as a byte count.
-        let (_, suf_str) = a.split_at(num_str.len());
+    fn parse_byte_count(input: &str) -> usize {
-        let num_usize = num_str
+        const SI_UNITS: &[char] = &['B', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'];
-            .parse::<usize>()
+
-            .expect("Error parsing buffer size: ");
+        let input = input.trim();
-        let suf_usize: usize = match suf_str.to_uppercase().as_str() {
+
-            // SI Units
+        let (num_str, si_unit) =
-            "B" => 1usize,
+            if input.ends_with(|c: char| SI_UNITS.contains(&c.to_ascii_uppercase())) {
-            "K" => 1000usize,
+                let mut chars = input.chars();
-            "M" => 1000000usize,
+                let si_suffix = chars.next_back().unwrap().to_ascii_uppercase();
-            "G" => 1000000000usize,
+                let si_unit = SI_UNITS.iter().position(|&c| c == si_suffix).unwrap();
-            // GNU regards empty human numeric values as K by default
+                let num_str = chars.as_str();
-            _ => 1000usize,
+                (num_str, si_unit)
+            } else {
+                (input, 1)
             };
-        num_usize * suf_usize
+
+        let num_usize: usize = num_str
+            .trim()
+            .parse()
+            .unwrap_or_else(|e| crash!(1, "failed to parse buffer size `{}`: {}", num_str, e));
+
+        num_usize.saturating_mul(1000usize.saturating_pow(si_unit as u32))
     }
 
     fn out_writer(&self) -> BufWriter<Box<dyn Write>> {
@@ -189,7 +199,6 @@ impl Default for GlobalSettings {
             zero_terminated: false,
             buffer_size: DEFAULT_BUF_SIZE,
             tmp_dir: PathBuf::new(),
-            ext_sort: false,
         }
     }
 }
@@ -941,28 +950,15 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
         env::set_var("RAYON_NUM_THREADS", &settings.threads);
     }
 
-    if matches.is_present(OPT_BUF_SIZE) {
+    settings.buffer_size = matches
-        settings.buffer_size = {
-            let input = matches
         .value_of(OPT_BUF_SIZE)
-                .map(String::from)
+        .map(GlobalSettings::parse_byte_count)
-                .unwrap_or(format!("{}", DEFAULT_BUF_SIZE));
+        .unwrap_or(DEFAULT_BUF_SIZE);
 
-            GlobalSettings::human_numeric_convert(&input)
+    settings.tmp_dir = matches
-        };
-        settings.ext_sort = true;
-    }
-
-    if matches.is_present(OPT_TMP_DIR) {
-        let result = matches
         .value_of(OPT_TMP_DIR)
-            .map(String::from)
+        .map(PathBuf::from)
-            .unwrap_or(format!("{}", env::temp_dir().display()));
+        .unwrap_or_else(env::temp_dir);
-        settings.tmp_dir = PathBuf::from(result);
-        settings.ext_sort = true;
-    } else {
-        settings.tmp_dir = env::temp_dir();
-    }
 
     settings.zero_terminated = matches.is_present(OPT_ZERO_TERMINATED);
     settings.merge = matches.is_present(OPT_MERGE);
@@ -1047,7 +1043,7 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
     exec(&files, &settings)
 }
 
-fn output_sorted_lines<'a>(iter: impl Iterator<Item = Line<'a>>, settings: &GlobalSettings) {
+fn output_sorted_lines<'a>(iter: impl Iterator<Item = &'a Line<'a>>, settings: &GlobalSettings) {
     if settings.unique {
         print_sorted(
             iter.dedup_by(|a, b| compare_by(a, b, &settings) == Ordering::Equal),
@@ -1067,34 +1063,10 @@ fn exec(files: &[String], settings: &GlobalSettings) -> i32 {
             crash!(1, "only one file allowed with -c");
         }
         return check::check(files.first().unwrap(), settings);
-    } else if settings.ext_sort {
+    } else {
         let mut lines = files.iter().filter_map(open);
 
-        let mut sorted = ext_sort(&mut lines, &settings);
+        ext_sort(&mut lines, &settings);
-        sorted.file_merger.write_all(settings);
-    } else {
-        let separator = if settings.zero_terminated { '\0' } else { '\n' };
-        let mut lines = vec![];
-        let mut full_string = String::new();
-
-        for mut file in files.iter().filter_map(open) {
-            crash_if_err!(1, file.read_to_string(&mut full_string));
-
-            if !full_string.ends_with(separator) {
-                full_string.push(separator);
-            }
-        }
-
-        if full_string.ends_with(separator) {
-            full_string.pop();
-        }
-
-        for line in full_string.split(if settings.zero_terminated { '\0' } else { '\n' }) {
-            lines.push(Line::create(line, &settings));
-        }
-
-        sort_by(&mut lines, &settings);
-        output_sorted_lines(lines.into_iter(), &settings);
     }
     0
 }
@@ -1366,7 +1338,7 @@ fn version_compare(a: &str, b: &str) -> Ordering {
     }
 }
 
-fn print_sorted<'a, T: Iterator<Item = Line<'a>>>(iter: T, settings: &GlobalSettings) {
+fn print_sorted<'a, T: Iterator<Item = &'a Line<'a>>>(iter: T, settings: &GlobalSettings) {
     let mut writer = settings.out_writer();
     for line in iter {
         line.print(&mut writer, settings);

tests/by-util/test_sort.rs

@@ -15,40 +15,35 @@ fn test_helper(file_name: &str, args: &str) {
         .stdout_is_fixture(format!("{}.expected.debug", file_name));
 }
 
-// FYI, the initialization size of our Line struct is 96 bytes.
-//
-// At very small buffer sizes, with that overhead we are certainly going
-// to overrun our buffer way, way, way too quickly because of these excess
-// bytes for the struct.
-//
-// For instance, seq 0..20000 > ...text = 108894 bytes
-// But overhead is 1920000 + 108894 = 2028894 bytes
-//
-// Or kjvbible-random.txt = 4332506 bytes, but minimum size of its
-// 99817 lines in memory * 96 bytes = 9582432 bytes
-//
-// Here, we test 108894 bytes with a 50K buffer
-//
 #[test]
-fn test_larger_than_specified_segment() {
+fn test_buffer_sizes() {
+    let buffer_sizes = [
+        "0", "50K", "50k", "1M", "100M", "1000G", "10T", "500E", "1Y",
+    ];
+    for buffer_size in &buffer_sizes {
         new_ucmd!()
             .arg("-n")
             .arg("-S")
-        .arg("50K")
+            .arg(buffer_size)
             .arg("ext_sort.txt")
             .succeeds()
             .stdout_is_fixture("ext_sort.expected");
+    }
 }
 
 #[test]
-fn test_smaller_than_specified_segment() {
+fn test_invalid_buffer_size() {
+    let buffer_sizes = ["asd", "100f"];
+    for invalid_buffer_size in &buffer_sizes {
         new_ucmd!()
-        .arg("-n")
             .arg("-S")
-        .arg("100M")
+            .arg(invalid_buffer_size)
-        .arg("ext_sort.txt")
+            .fails()
-        .succeeds()
+            .stderr_only(format!(
-        .stdout_is_fixture("ext_sort.expected");
+                "sort: error: failed to parse buffer size `{}`: invalid digit found in string",
+                invalid_buffer_size
+            ));
+    }
 }
 
 #[test]