[GFS2] Shrink gfs2_inode memory by half
Here is something I spotted (while looking for something entirely
different) the other day.
Rather than using a completion in each and every struct gfs2_holder,
this removes it in favour of hashed wait queues, thus saving a
considerable amount of memory both on the stack (where a number of
gfs2_holder structures are allocated) and in particular in the
gfs2_inode which has 8 gfs2_holder structures embedded within it.
As a result on x86_64 the gfs2_inode shrinks from 2488 bytes to
1912 bytes, a saving of 576 bytes per inode (no thats not a typo!).
In actual practice we get a much better result than that since
now that a gfs2_inode is under the 2048 byte barrier, we get two
per 4k slab page effectively halving the amount of memory required
to store gfs2_inodes.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 9114851..a24c4af 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -128,6 +128,7 @@
HIF_HOLDER = 6,
HIF_FIRST = 7,
HIF_ABORTED = 9,
+ HIF_WAIT = 10,
};
struct gfs2_holder {
@@ -140,7 +141,6 @@
int gh_error;
unsigned long gh_iflags;
- struct completion gh_wait;
unsigned long gh_ip;
};
