From 028af2764622d489583cd88935cd1d2a7fbe8248 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Tue, 29 Oct 2019 04:32:55 -0400
Subject: [PATCH] mention LRU list a bit more in comments.
---
kernel/bio.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/bio.c b/kernel/bio.c
index a1074f2..60d91a6 100644
--- a/kernel/bio.c
+++ b/kernel/bio.c
@@ -28,7 +28,8 @@ struct {
struct buf buf[NBUF];
// Linked list of all buffers, through prev/next.
- // head.next is most recently used.
+ // Sorted by how recently the buffer was used.
+ // head.next is most recent, head.prev is least.
struct buf head;
} bcache;
@@ -71,7 +72,8 @@ bget(uint dev, uint blockno)
}
}
- // Not cached; recycle an unused buffer.
+ // Not cached.
+ // Recycle the least recently used (LRU) unused buffer.
for(b = bcache.head.prev; b != &bcache.head; b = b->prev){
if(b->refcnt == 0) {
b->dev = dev;
@@ -110,7 +112,7 @@ bwrite(struct buf *b)
}
// Release a locked buffer.
-// Move to the head of the MRU list.
+// Move to the head of the most-recently-used list.
void
brelse(struct buf *b)
{