tiered compaction: introduce PAGE_SZ constant and use it (#7785)

pointed out by @problame : we use the literal 8192 instead of a properly
defined constant. replace the literal by a PAGE_SZ constant.

pageserver/compaction/src/bin/compaction-simulator.rs

@@ -1,4 +1,5 @@
 use clap::{Parser, Subcommand};
+use pageserver_compaction::helpers::PAGE_SZ;
 use pageserver_compaction::simulator::MockTimeline;
 use rand::Rng;
 use std::io::Write;
@@ -51,7 +52,7 @@ async fn simulate(cmd: &SimulateCmd, results_path: &Path) -> anyhow::Result<()>
     let mut executor = MockTimeline::new();
 
     // Convert the logical size in MB into a key range.
-    let key_range = 0..((cmd.logical_size * 1024 * 1024) / 8192);
+    let key_range = 0..((cmd.logical_size * 1024 * 1024) / PAGE_SZ);
     //let key_range = u64::MIN..u64::MAX;
     println!(
         "starting simulation with key range {:016X}-{:016X}",

pageserver/compaction/src/compact_tiered.rs

@@ -25,7 +25,7 @@ use std::collections::{HashSet, VecDeque};
 use std::ops::Range;
 
 use crate::helpers::{
-    accum_key_values, keyspace_total_size, merge_delta_keys_buffered, overlaps_with,
+    accum_key_values, keyspace_total_size, merge_delta_keys_buffered, overlaps_with, PAGE_SZ,
 };
 use crate::interface::*;
 use utils::lsn::Lsn;
@@ -379,7 +379,7 @@ where
                 .get_keyspace(&job.key_range, job.lsn_range.end, ctx)
                 .await?,
             &self.shard_identity,
-        ) * 8192;
+        ) * PAGE_SZ;
 
         let wal_size = job
             .input_layers
@@ -441,7 +441,7 @@ where
         let mut window = KeyspaceWindow::new(
             E::Key::MIN..E::Key::MAX,
             keyspace,
-            self.target_file_size / 8192,
+            self.target_file_size / PAGE_SZ,
         );
         while let Some(key_range) = window.choose_next_image(&self.shard_identity) {
             new_jobs.push(CompactionJob::<E> {

pageserver/compaction/src/helpers.rs

@@ -16,6 +16,8 @@ use std::pin::Pin;
 use std::task::{ready, Poll};
 use utils::lsn::Lsn;
 
+pub const PAGE_SZ: u64 = 8192;
+
 pub fn keyspace_total_size<K>(
     keyspace: &CompactionKeySpace<K>,
     shard_identity: &ShardIdentity,

pageserver/compaction/src/simulator.rs

@@ -14,6 +14,7 @@ use std::ops::Range;
 use std::sync::Arc;
 use std::sync::Mutex;
 
+use crate::helpers::PAGE_SZ;
 use crate::helpers::{merge_delta_keys, overlaps_with};
 
 use crate::interface;
@@ -509,7 +510,7 @@ impl interface::CompactionJobExecutor for MockTimeline {
         let new_layer = Arc::new(MockImageLayer {
             key_range: key_range.clone(),
             lsn_range: lsn..lsn,
-            file_size: accum_size * 8192,
+            file_size: accum_size * PAGE_SZ,
             deleted: Mutex::new(false),
         });
         info!(