Re: [PATCH] read-cache.c: fix index memory allocation

Am 25.10.2011 02:01, schrieb Nguyen Thai Ngoc Duy:

On Tue, Oct 25, 2011 at 10:34 AM, Nguyen Thai Ngoc Duy
[off-list ref] wrote:

quoted

"git status" is slow. If your changes causes slowdown, it won't likely
stand out while other fast commands may show (read_cache() is used in
nearly all commands). So I tested using the following patch.

The result on linux-2.6 shows about 10-20 us slowdown per each
read_cache() call (30-40 us on webkit, ~50k files) I think your patch
is good enough :-)

That was with -O0 by the way. valgrind/massif shows about 200kb memory
more with your patch on webkit repository (7.497 MB vs 7.285 MB),
using the same test, so memory overhead is ok too.

We can reduce that a bit -- unless block allocation of index entries
is still done somewhere.

-- >8 --
Subject: [PATCH 2/1] cache.h: put single NUL at end of struct cache_entry

Since in-memory index entries are allocated individually now, the
variable slack at the end meant to provide an eight byte alignment
is not needed anymore.  Have a single NUL instead.  This saves zero
to seven bytes for an entry, depending on its filename length.

Signed-off-by: Rene Scharfe <redacted>
---

 cache.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/cache.h b/cache.h
index ec0e571..bd106b5 100644
--- a/cache.h
+++ b/cache.h

@@ -306,7 +306,7 @@ static inline unsigned int canon_mode(unsigned int mode)
 }
 
 #define flexible_size(STRUCT,len) ((offsetof(struct STRUCT,name) + (len) + 8) & ~7)
-#define cache_entry_size(len) flexible_size(cache_entry,len)
+#define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)
 #define ondisk_cache_entry_size(len) flexible_size(ondisk_cache_entry,len)
 #define ondisk_cache_entry_extended_size(len) flexible_size(ondisk_cache_entry_extended,len)
 

-- 
1.7.7