blktrace support: speedup reading of data
We used to read in data in really small chunks (48 bytes at the time,
the size of the trace). This is really slow for large traces, so
add a fifo frontend to refill the cache in much larger sizes.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fifo.c b/fifo.c
new file mode 100644
index 0000000..1e55b63
--- /dev/null
+++ b/fifo.c
@@ -0,0 +1,88 @@
+/*
+ * A simple kernel FIFO implementation.
+ *
+ * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "fifo.h"
+
+struct fifo *fifo_alloc(unsigned int size)
+{
+ struct fifo *fifo;
+
+ fifo = malloc(sizeof(struct fifo));
+ if (!fifo)
+ return 0;
+
+ fifo->buffer = malloc(size);
+ fifo->size = size;
+ fifo->in = fifo->out = 0xffff0000;
+
+ return fifo;
+}
+
+void fifo_free(struct fifo *fifo)
+{
+ free(fifo->buffer);
+ free(fifo);
+}
+
+unsigned int fifo_put(struct fifo *fifo, void *buffer, unsigned int len)
+{
+ unsigned int l;
+
+ len = min(len, fifo->size - fifo->in + fifo->out);
+
+ /* first put the data starting from fifo->in to buffer end */
+ l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
+ memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
+
+ /* then put the rest (if any) at the beginning of the buffer */
+ memcpy(fifo->buffer, buffer + l, len - l);
+
+ /*
+ * Ensure that we add the bytes to the fifo -before-
+ * we update the fifo->in index.
+ */
+
+ fifo->in += len;
+
+ return len;
+}
+
+unsigned int fifo_get(struct fifo *fifo, void *buffer, unsigned int len)
+{
+ unsigned int l;
+
+ len = min(len, fifo->in - fifo->out);
+
+ /* first get the data from fifo->out until the end of the buffer */
+ l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
+ memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
+
+ /* then get the rest (if any) from the beginning of the buffer */
+ memcpy(buffer + l, fifo->buffer, len - l);
+
+ fifo->out += len;
+
+ return len;
+}