Reduce task params memory pressure by sending seed instead of entire …

…RNG (in theory this also improves output quality as we don't ever have RNGs in the same state)

Signed-off-by: Alex Saveau <saveau.alexandre@gmail.com>

README.md

@@ -42,7 +42,7 @@ Generate ~10_000 files with ~1 MB of random data spread across them:
 ```console
 $ ftzz ./with_data -n 10K -b 1M
 About 10,000 files will be generated in approximately 1,000 directories distributed across a tree of maximum depth 5 where each directory contains approximately 4 other directories. Each file will contain approximately 100 bytes of random data.
-Created 9,419 files (929.4 KB) across 1,138 directories.
+Created 9,652 files (960.1 KB) across 930 directories.
 
 ```
 

src/core/file_contents.rs

@@ -1,17 +1,23 @@
 use std::{fs::File, io, io::Read};
 
 use cfg_if::cfg_if;
-use rand::RngCore;
+use rand::{RngCore, SeedableRng};
 use rand_distr::Normal;
+use rand_xoshiro::Xoshiro256PlusPlus;
 
 use crate::{core::sample_truncated, utils::FastPathBuf};
 
 pub trait FileContentsGenerator {
+    type State;
+
+    fn initialize(&self) -> Self::State;
+
     fn create_file(
         &mut self,
         file: &mut FastPathBuf,
         file_num: usize,
         retryable: bool,
+        state: &mut Self::State,
     ) -> io::Result<u64>;
 
     fn byte_counts_pool_return(self) -> Option<Vec<u64>>;
@@ -20,8 +26,18 @@ pub trait FileContentsGenerator {
 pub struct NoGeneratedFileContents;
 
 impl FileContentsGenerator for NoGeneratedFileContents {
+    type State = ();
+
+    fn initialize(&self) -> Self::State {}
+
     #[inline]
-    fn create_file(&mut self, file: &mut FastPathBuf, _: usize, _: bool) -> io::Result<u64> {
+    fn create_file(
+        &mut self,
+        file: &mut FastPathBuf,
+        _: usize,
+        _: bool,
+        (): &mut Self::State,
+    ) -> io::Result<u64> {
         cfg_if! {
             if #[cfg(any(not(unix), miri))] {
                 File::create(file).map(|_| 0)
@@ -59,24 +75,33 @@ impl FileContentsGenerator for NoGeneratedFileContents {
     }
 }
 
-pub struct OnTheFlyGeneratedFileContents<R: RngCore> {
+pub struct OnTheFlyGeneratedFileContents {
     pub num_bytes_distr: Normal<f64>,
-    pub random: R,
+    pub seed: u64,
     pub fill_byte: Option<u8>,
 }
 
-impl<R: RngCore + 'static> FileContentsGenerator for OnTheFlyGeneratedFileContents<R> {
+impl FileContentsGenerator for OnTheFlyGeneratedFileContents {
+    type State = Xoshiro256PlusPlus;
+
+    fn initialize(&self) -> Self::State {
+        let Self { seed, .. } = *self;
+
+        Xoshiro256PlusPlus::seed_from_u64(seed)
+    }
+
     #[inline]
     #[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
     fn create_file(
         &mut self,
         file: &mut FastPathBuf,
         file_num: usize,
         retryable: bool,
+        random: &mut Self::State,
     ) -> io::Result<u64> {
         let Self {
             ref num_bytes_distr,
-            ref mut random,
+            seed: _,
             fill_byte,
         } = *self;
 
@@ -109,7 +134,7 @@ impl<R: RngCore + 'static> FileContentsGenerator for OnTheFlyGeneratedFileConten
                 Ok(num_bytes)
             })
         } else {
-            NoGeneratedFileContents.create_file(file, file_num, retryable)
+            NoGeneratedFileContents.create_file(file, file_num, retryable, &mut ())
         }
     }
 
@@ -118,23 +143,32 @@ impl<R: RngCore + 'static> FileContentsGenerator for OnTheFlyGeneratedFileConten
     }
 }
 
-pub struct PreDefinedGeneratedFileContents<R: RngCore> {
+pub struct PreDefinedGeneratedFileContents {
     pub byte_counts: Vec<u64>,
-    pub random: R,
+    pub seed: u64,
     pub fill_byte: Option<u8>,
 }
 
-impl<R: RngCore + 'static> FileContentsGenerator for PreDefinedGeneratedFileContents<R> {
+impl FileContentsGenerator for PreDefinedGeneratedFileContents {
+    type State = Xoshiro256PlusPlus;
+
+    fn initialize(&self) -> Self::State {
+        let Self { seed, .. } = *self;
+
+        Xoshiro256PlusPlus::seed_from_u64(seed)
+    }
+
     #[inline]
     fn create_file(
         &mut self,
         file: &mut FastPathBuf,
         file_num: usize,
         retryable: bool,
+        random: &mut Self::State,
     ) -> io::Result<u64> {
         let Self {
             ref byte_counts,
-            ref mut random,
+            seed: _,
             fill_byte,
         } = *self;
 
@@ -144,7 +178,7 @@ impl<R: RngCore + 'static> FileContentsGenerator for PreDefinedGeneratedFileCont
                 .and_then(|f| write_bytes(f, num_bytes, (fill_byte, random)))
                 .map(|()| num_bytes)
         } else {
-            NoGeneratedFileContents.create_file(file, file_num, retryable)
+            NoGeneratedFileContents.create_file(file, file_num, retryable, &mut ())
         }
     }
 

src/core/files.rs

@@ -73,13 +73,14 @@ fn create_files(
     file: &mut FastPathBuf,
     contents: &mut impl FileContentsGenerator,
 ) -> Result<u64, io::Error> {
+    let mut state = contents.initialize();
     let mut bytes_written = 0;
 
     let mut start_file = 0;
     if num_files > 0 {
         with_file_name(offset, |s| file.push(s));
 
-        match contents.create_file(file, 0, true) {
+        match contents.create_file(file, 0, true, &mut state) {
             Ok(bytes) => {
                 bytes_written += bytes;
                 start_file += 1;
@@ -104,7 +105,7 @@ fn create_files(
         with_file_name(i + offset, |s| file.push(s));
 
         bytes_written += contents
-            .create_file(file, i.try_into().unwrap_or(usize::MAX), false)
+            .create_file(file, i.try_into().unwrap_or(usize::MAX), false, &mut state)
             .attach_printable_lazy(|| format!("Failed to create file {file:?}"))?;
 
         file.pop();

src/core/tasks.rs

@@ -155,7 +155,7 @@ impl<R: RngCore + Clone + Send + 'static> TaskGenerator for DynamicGenerator<R>
             queue(
                 build_params!(OnTheFlyGeneratedFileContents {
                     num_bytes_distr,
-                    random: random.clone(),
+                    seed: random.next_u64(),
                     fill_byte,
                 }),
                 false,
@@ -371,7 +371,7 @@ impl<R: RngCore + Clone + Send + 'static> StaticGenerator<R> {
                     queue(
                         build_params!(PreDefinedGeneratedFileContents {
                             byte_counts,
-                            random: random.clone(),
+                            seed: random.next_u64(),
                             fill_byte,
                         }),
                         done,
@@ -383,7 +383,7 @@ impl<R: RngCore + Clone + Send + 'static> StaticGenerator<R> {
                 queue(
                     build_params!(OnTheFlyGeneratedFileContents {
                         num_bytes_distr,
-                        random: random.clone(),
+                        seed: random.next_u64(),
                         fill_byte,
                     }),
                     done,

testdata/cmds/examples.md

@@ -3,7 +3,7 @@
 ```console
 $ ftzz -n 1K -b 100 --files-exact --bytes-exact all-exact-explicit
 Exactly 1,000 files will be generated in approximately 1,000 directories distributed across a tree of maximum depth 5 where each directory contains approximately 4 other directories. Each file will contain approximately 0 bytes of random data totaling exactly 100 bytes.
-Created 1,000 files (100 B) across 788 directories.
+Created 1,000 files (100 B) across 506 directories.
 
 ```
 

testdata/generator/advanced_create_files_bytes_100000_10000_0_1.stdout

@@ -1,5 +1,5 @@
 About 10,000 files will be generated in approximately 1 directory distributed across a tree of maximum depth 0 where each directory contains approximately 0 other directories. Each file will contain approximately 10 bytes of random data.
-Created 9,024 files (90.2 KB) across 0 directories.
+Created 9,024 files (90.8 KB) across 0 directories.
 
 /0
 /1
@@ -9026,4 +9026,4 @@ Created 9,024 files (90.2 KB) across 0 directories.
 /998
 /999
 
-0x8167745075cde23d
+0xfffb6f2d2deef4d1

testdata/generator/advanced_create_files_bytes_100000_10000_0_100.stdout

@@ -1,5 +1,5 @@
 About 10,000 files will be generated in approximately 1 directory distributed across a tree of maximum depth 0 where each directory contains approximately 0 other directories. Each file will contain approximately 10 bytes of random data.
-Created 9,024 files (90.2 KB) across 0 directories.
+Created 9,024 files (90.8 KB) across 0 directories.
 
 /0
 /1
@@ -9026,4 +9026,4 @@ Created 9,024 files (90.2 KB) across 0 directories.
 /998
 /999
 
-0x8167745075cde23d
+0xfffb6f2d2deef4d1

testdata/generator/advanced_create_files_bytes_100000_10000_0_1000.stdout

@@ -1,5 +1,5 @@
 About 10,000 files will be generated in approximately 1 directory distributed across a tree of maximum depth 0 where each directory contains approximately 0 other directories. Each file will contain approximately 10 bytes of random data.
-Created 9,024 files (90.2 KB) across 0 directories.
+Created 9,024 files (90.8 KB) across 0 directories.
 
 /0
 /1
@@ -9026,4 +9026,4 @@ Created 9,024 files (90.2 KB) across 0 directories.
 /998
 /999
 
-0x8167745075cde23d
+0xfffb6f2d2deef4d1