From 4990aadc4cbb872cb71acdc0ca842eacb86f1362 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 20 Apr 2005 12:16:57 -0700 Subject: [PATCH] Speed up index file writing by chunking it nicely. No point in making 17,000 small writes when you can make just a couple of hundred nice 8kB writes instead and save a lot of time. --- read-cache.c | 43 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 4 deletions(-) diff --git a/read-cache.c b/read-cache.c index bfa2de767..c3beb6748 100644 --- a/read-cache.c +++ b/read-cache.c @@ -227,6 +227,42 @@ unmap: return error("verify header failed"); } +#define WRITE_BUFFER_SIZE 8192 +static char write_buffer[WRITE_BUFFER_SIZE]; +static unsigned long write_buffer_len; + +static int ce_write(int fd, void *data, unsigned int len) +{ + while (len) { + unsigned int buffered = write_buffer_len; + unsigned int partial = WRITE_BUFFER_SIZE - buffered; + if (partial > len) + partial = len; + memcpy(write_buffer + buffered, data, partial); + buffered += partial; + if (buffered == WRITE_BUFFER_SIZE) { + if (write(fd, write_buffer, WRITE_BUFFER_SIZE) != WRITE_BUFFER_SIZE) + return -1; + buffered = 0; + } + write_buffer_len = buffered; + len -= partial; + data += partial; + } + return 0; +} + +static int ce_flush(int fd) +{ + unsigned int left = write_buffer_len; + if (left) { + write_buffer_len = 0; + if (write(fd, write_buffer, left) != left) + return -1; + } + return 0; +} + int write_cache(int newfd, struct cache_entry **cache, int entries) { SHA_CTX c; @@ -246,14 +282,13 @@ int write_cache(int newfd, struct cache_entry **cache, int entries) } SHA1_Final(hdr.sha1, &c); - if (write(newfd, &hdr, sizeof(hdr)) != sizeof(hdr)) + if (ce_write(newfd, &hdr, sizeof(hdr)) < 0) return -1; for (i = 0; i < entries; i++) { struct cache_entry *ce = cache[i]; - int size = ce_size(ce); - if (write(newfd, ce, size) != size) + if (ce_write(newfd, ce, ce_size(ce)) < 0) return -1; } - return 0; + return ce_flush(newfd); } -- 2.26.2