Merge small pipe writes into the write buffers

diff --git a/fs/pipe.c b/fs/pipe.c
index f1c5de710cd687d9334c8bcda69feea9d7171884..eb7df855732ec5832c44ec50475cd3e12e6ca490 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -203,6 +203,27 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
        ret = 0;
        down(PIPE_SEM(*inode));
        info = inode->i_pipe;
+
+       /* We try to merge small writes */
+       if (info->nrbufs && total_len < PAGE_SIZE) {
+               int lastbuf = (info->curbuf + info->nrbufs - 1) & (PIPE_BUFFERS-1);
+               struct pipe_buffer *buf = info->bufs + lastbuf;
+               int offset = buf->offset + buf->len;
+               if (offset + total_len <= PAGE_SIZE) {
+                       struct page *page = buf->page;
+                       int error = pipe_iov_copy_from_user(offset + kmap(page), iov, total_len);
+                       kunmap(page);
+                       ret = error;
+                       do_wakeup = 1;
+                       if (error)
+                               goto out;
+                       buf->len += total_len;
+                       ret = total_len;
+                       goto out;
+               }
+                       
+       }
+
        for (;;) {
                int bufs;
                if (!PIPE_READERS(*inode)) {
@@ -270,6 +291,7 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
                pipe_wait(inode);
                PIPE_WAITING_WRITERS(*inode)--;
        }
+out:
        up(PIPE_SEM(*inode));
        if (do_wakeup) {
                wake_up_interruptible(PIPE_WAIT(*inode));