Re: [PATCH] write-tree performance problems

From

Linus Torvalds <torvalds@osdl.org>

Date

Apr 20, 2005, 15:40 UTC

Message-ID

<Pine.LNX.4.58.0504200833580.6467@ppc970.osdl.org>

In-Reply-To

<200504201122.35448.mason@suse.com>

On Wed, 20 Apr 2005, Chris Mason wrote:

> 
> Thanks for looking at this.  Your new tree is faster, it gets the commit 100 
> patches time down from 1m5s to 50s.

		Linus
---
sha1_file.c: 40c00b77d0e52b31dda1696f10026fe6f92bc082

--- a/sha1_file.c
+++ b/sha1_file.c
@@ -173,12 +173,27 @@ int write_sha1_file(char *buf, unsigned 
 	z_stream stream;
 	unsigned char sha1[20];
 	SHA_CTX c;
+	char *filename;
+	int fd;
 
 	/* Sha1.. */
 	SHA1_Init(&c);
 	SHA1_Update(&c, buf, len);
 	SHA1_Final(sha1, &c);
 
+	filename = sha1_file_name(sha1);
+	fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
+	if (fd < 0) {
+		if (errno != EEXIST)
+			return -1;
+
+		/*
+		 * We might do collision checking here, but we'd need to
+		 * uncompress the old file and check it. Later.
+		 */
+		return 0;
+	}
+
 	/* Set it up */
 	memset(&stream, 0, sizeof(stream));
 	deflateInit(&stream, Z_BEST_COMPRESSION);
@@ -195,8 +210,10 @@ int write_sha1_file(char *buf, unsigned 
 	deflateEnd(&stream);
 	size = stream.total_out;
 
-	if (write_sha1_buffer(sha1, compressed, size) < 0)
-		return -1;
+	if (write(fd, compressed, size) != size)
+		die("unable to write file");
+	close(fd);
+		
 	if (returnsha1)
 		memcpy(returnsha1, sha1, 20);
 	return 0;