2003-05-05 16:43:49

by Mikael Starvik

Subject: [PATCH 2.4.20] alloc_kiovec performance improvement

alloc_kiovec always allocates 1024 buffer heads which is a waste
with performance in the cases when the buffers aren't used.

The patch below adds variants that doesn't allocate the buffer heads.

A similar approach would be to introduce a common function with
a flag that indicates if buffer heads should be allocated.

/Mikael

diff -Nurp linux-2.4.20/fs/iobuf.c linux-2.4.20-local/fs/iobuf.c
--- linux-2.4.20/fs/iobuf.c Fri Nov 29 00:53:15 2002
+++ linux-2.4.20-local/fs/iobuf.c Mon May 5 18:35:12 2003
@@ -114,6 +114,29 @@ nomem:
return -ENOMEM;
}

+int alloc_kiovec_nobhs(int nr, struct kiobuf **bufp)
+{
+ int i;
+ struct kiobuf *iobuf;
+
+ for (i = 0; i < nr; i++) {
+ iobuf = kmem_cache_alloc(kiobuf_cachep, GFP_KERNEL);
+ if (unlikely(!iobuf))
+ goto nomem;
+ if (unlikely(kiobuf_init(iobuf)))
+ goto nomem2;
+ bufp[i] = iobuf;
+ }
+
+ return 0;
+
+nomem2:
+ kmem_cache_free(kiobuf_cachep, iobuf);
+nomem:
+ free_kiovec_nobhs(i, bufp);
+ return -ENOMEM;
+}
+
void free_kiovec(int nr, struct kiobuf **bufp)
{
int i;
@@ -128,6 +151,20 @@ void free_kiovec(int nr, struct kiobuf *
kmem_cache_free(kiobuf_cachep, bufp[i]);
}
}
+
+void free_kiovec_nobhs(int nr, struct kiobuf **bufp)
+{
+ int i;
+ struct kiobuf *iobuf;
+
+ for (i = 0; i < nr; i++) {
+ iobuf = bufp[i];
+ if (iobuf->locked)
+ unlock_kiovec(1, &iobuf);
+ kfree(iobuf->maplist);
+ kmem_cache_free(kiobuf_cachep, bufp[i]);
+ }
+}

int expand_kiobuf(struct kiobuf *iobuf, int wanted)
{
diff -Nurp linux-2.4.20/include/linux/iobuf.h linux-2.4.20-local/include/linux/iobuf.h
--- linux-2.4.20/include/linux/iobuf.h Fri Nov 29 00:53:15 2002
+++ linux-2.4.20-local/include/linux/iobuf.h Mon May 5 18:35:51 2003
@@ -64,7 +64,9 @@ void mark_dirty_kiobuf(struct kiobuf *io
void end_kio_request(struct kiobuf *, int);
void simple_wakeup_kiobuf(struct kiobuf *);
int alloc_kiovec(int nr, struct kiobuf **);
+int alloc_kiovec_nobhs(int nr, struct kiobuf **);
void free_kiovec(int nr, struct kiobuf **);
+void free_kiovec_nobhs(int nr, struct kiobuf **);
int expand_kiobuf(struct kiobuf *, int);
void kiobuf_wait_for_io(struct kiobuf *);
extern int alloc_kiobuf_bhs(struct kiobuf *);
diff -Nurp linux-2.4.20/kernel/ksyms.c linux-2.4.20-local/kernel/ksyms.c
--- linux-2.4.20/kernel/ksyms.c Fri Nov 29 00:53:15 2002
+++ linux-2.4.20-local/kernel/ksyms.c Mon May 5 18:36:25 2003
@@ -410,7 +410,9 @@ EXPORT_SYMBOL(__br_write_unlock);

/* Kiobufs */
EXPORT_SYMBOL(alloc_kiovec);
+EXPORT_SYMBOL(alloc_kiovec_nobhs);
EXPORT_SYMBOL(free_kiovec);
+EXPORT_SYMBOL(free_kiovec_nobhs);
EXPORT_SYMBOL(expand_kiobuf);

EXPORT_SYMBOL(map_user_kiobuf);

2003-05-06 11:41:24

by Alan

Subject: Re: [PATCH 2.4.20] alloc_kiovec performance improvement

On Llu, 2003-05-05 at 17:54, Mikael Starvik wrote:
> alloc_kiovec always allocates 1024 buffer heads which is a waste
> with performance in the cases when the buffers aren't used.

See the patches in -ac that came from tuning Oracle performance.