new file mode 100644
--- /dev/null
+++ b/src/os/unix/ngx_writev_chain.c
@@ -0,0 +1,160 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+
+
+#define NGX_IOVS  8
+
+
+ngx_chain_t *ngx_writev_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
+{
+    u_char        *prev;
+    ssize_t        n, size;
+    off_t          send, sprev, sent;
+    ngx_uint_t     eintr, complete;
+    ngx_err_t      err;
+    ngx_array_t    vec;
+    ngx_chain_t   *cl;
+    ngx_event_t   *wev;
+    struct iovec  *iov, iovs[NGX_IOVS];
+
+    wev = c->write;
+
+    if (!wev->ready) {
+        return in;
+    }
+
+#if (HAVE_KQUEUE)
+
+    if ((ngx_event_flags & NGX_HAVE_KQUEUE_EVENT) && wev->pending_eof) {
+        ngx_log_error(NGX_LOG_INFO, c->log, wev->kq_errno,
+                      "kevent() reported about an closed connection");
+
+        wev->error = 1;
+        return NGX_CHAIN_ERROR;
+    }
+
+#endif
+
+    send = 0;
+    complete = 0;
+
+    vec.elts = iovs;
+    vec.size = sizeof(struct iovec);
+    vec.nalloc = NGX_IOVS;
+    vec.pool = c->pool;
+
+    for ( ;; ) {
+        prev = NULL;
+        iov = NULL;
+        eintr = 0;
+        sprev = send;
+
+        vec.nelts = 0;
+
+        /* create the iovec and coalesce the neighbouring bufs */
+
+        for (cl = in; cl && vec.nelts < IOV_MAX && send < limit; cl = cl->next)
+        {
+            if (ngx_buf_special(cl->buf)) {
+                continue;
+            }
+
+            size = cl->buf->last - cl->buf->pos;
+
+            if (send + size > limit) {
+                size = limit - send;
+            }
+
+            if (prev == cl->buf->pos) {
+                iov->iov_len += size;
+
+            } else {
+                if (!(iov = ngx_array_push(&vec))) {
+                    return NGX_CHAIN_ERROR;
+                }
+
+                iov->iov_base = (void *) cl->buf->pos;
+                iov->iov_len = size;
+            }
+
+            prev = cl->buf->pos + size;
+            send += size;
+        }
+
+        n = writev(c->fd, vec.elts, vec.nelts);
+
+        if (n == -1) {
+            err = ngx_errno;
+
+            if (err == NGX_EAGAIN || err == NGX_EINTR) {
+                if (err == NGX_EINTR) {
+                    eintr = 1;
+                }
+
+                ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, err,
+                               "writev() not ready");
+
+            } else {
+                wev->error = 1;
+                ngx_connection_error(c, err, "writev() failed");
+                return NGX_CHAIN_ERROR;
+            }
+        }
+
+        sent = n > 0 ? n : 0;
+
+        ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                       "writev: " OFF_T_FMT, sent);
+
+        if (send - sprev == sent) {
+            complete = 1;
+        }
+
+        c->sent += sent;
+
+        for (cl = in; cl && sent > 0; cl = cl->next) {
+            if (ngx_buf_special(cl->buf)) {
+                continue;
+            }
+
+            if (sent == 0) {
+                break;
+            }
+
+            size = cl->buf->last - cl->buf->pos;
+
+            if (sent >= size) {
+                sent -= size;
+                cl->buf->pos = cl->buf->last;
+
+                continue;
+            }
+
+            cl->buf->pos += sent;
+
+            break;
+        }
+
+        if (eintr) {
+            continue;
+        }
+
+        if (!complete) {
+            wev->ready = 0;
+            return cl;
+        }
+
+        if (send >= limit || cl == NULL) {
+            return cl;
+        }
+
+        in = cl;
+    }
+}