Added support for offloading Linux sendfile() in thread pools.

src/core/ngx_connection.h

@@ -184,6 +184,10 @@ struct ngx_connection_s {
     unsigned            busy_count:2;
 #endif
 
+#if (NGX_THREADS)
+    ngx_thread_task_t  *sendfile_task;
+#endif
+
 #if (NGX_OLD_THREADS)
     ngx_atomic_t        lock;
 #endif

src/os/unix/ngx_linux_sendfile_chain.c

@@ -13,6 +13,18 @@
 static ssize_t ngx_linux_sendfile(ngx_connection_t *c, ngx_buf_t *file,
     size_t size);
 
+#if (NGX_THREADS)
+#include <ngx_thread_pool.h>
+
+#if !(NGX_HAVE_SENDFILE64)
+#error sendfile64() is required!
+#endif
+
+static ngx_int_t ngx_linux_sendfile_thread(ngx_connection_t *c, ngx_buf_t *file,
+    size_t size, size_t *sent);
+static void ngx_linux_sendfile_thread_handler(void *data, ngx_log_t *log);
+#endif
+
 
 /*
  * On Linux up to 2.4.21 sendfile() (syscall #187) works with 32-bit
@@ -35,8 +47,8 @@ ngx_chain_t *
 ngx_linux_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
 {
     int            tcp_nodelay;
-    off_t          send, prev_send, sent;
+    off_t          send, prev_send;
-    size_t         file_size;
+    size_t         file_size, sent;
     ssize_t        n;
     ngx_err_t      err;
     ngx_buf_t     *file;
@@ -44,6 +56,10 @@ ngx_linux_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
     ngx_chain_t   *cl;
     ngx_iovec_t    header;
     struct iovec   headers[NGX_IOVS_PREALLOCATE];
+#if (NGX_THREADS)
+    ngx_int_t      rc;
+    ngx_uint_t     thread_handled, thread_complete;
+#endif
 
     wev = c->write;
 
@@ -66,6 +82,10 @@ ngx_linux_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
 
     for ( ;; ) {
         prev_send = send;
+#if (NGX_THREADS)
+        thread_handled = 0;
+        thread_complete = 0;
+#endif
 
         /* create the iovec and coalesce the neighbouring bufs */
 
@@ -158,14 +178,39 @@ ngx_linux_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
                 return NGX_CHAIN_ERROR;
             }
 #endif
-            n = ngx_linux_sendfile(c, file, file_size);
 
-            if (n == NGX_ERROR) {
+#if (NGX_THREADS)
-                return NGX_CHAIN_ERROR;
+            if (file->file->thread_handler) {
+                rc = ngx_linux_sendfile_thread(c, file, file_size, &sent);
+
+                switch (rc) {
+                case NGX_OK:
+                    thread_handled = 1;
+                    break;
+
+                case NGX_DONE:
+                    thread_complete = 1;
+                    break;
+
+                case NGX_AGAIN:
+                    break;
+
+                default: /* NGX_ERROR */
+                    return NGX_CHAIN_ERROR;
+                }
+
+            } else
+#endif
+            {
+                n = ngx_linux_sendfile(c, file, file_size);
+
+                if (n == NGX_ERROR) {
+                    return NGX_CHAIN_ERROR;
+                }
+
+                sent = (n == NGX_AGAIN) ? 0 : n;
             }
 
-            sent = (n == NGX_AGAIN) ? 0 : n;
-
         } else {
             n = ngx_writev(c, &header);
 
@@ -180,7 +225,17 @@ ngx_linux_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
 
         in = ngx_chain_update_sent(in, sent);
 
-        if (send - prev_send != sent) {
+        if ((size_t) (send - prev_send) != sent) {
+#if (NGX_THREADS)
+            if (thread_handled) {
+                return in;
+            }
+
+            if (thread_complete) {
+                send = prev_send + sent;
+                continue;
+            }
+#endif
             wev->ready = 0;
             return in;
         }
@@ -242,3 +297,123 @@ eintr:
 
     return n;
 }
+
+
+#if (NGX_THREADS)
+
+typedef struct {
+    ngx_buf_t     *file;
+    ngx_socket_t   socket;
+    size_t         size;
+
+    size_t         sent;
+    ngx_err_t      err;
+} ngx_linux_sendfile_ctx_t;
+
+
+static ngx_int_t
+ngx_linux_sendfile_thread(ngx_connection_t *c, ngx_buf_t *file, size_t size,
+    size_t *sent)
+{
+    ngx_uint_t                 flags;
+    ngx_event_t               *wev;
+    ngx_thread_task_t         *task;
+    ngx_linux_sendfile_ctx_t  *ctx;
+
+    ngx_log_debug3(NGX_LOG_DEBUG_CORE, c->log, 0,
+                   "linux sendfile thread: %d, %uz, %O",
+                   file->file->fd, size, file->file_pos);
+
+    task = c->sendfile_task;
+
+    if (task == NULL) {
+        task = ngx_thread_task_alloc(c->pool, sizeof(ngx_linux_sendfile_ctx_t));
+        if (task == NULL) {
+            return NGX_ERROR;
+        }
+
+        task->handler = ngx_linux_sendfile_thread_handler;
+
+        c->sendfile_task = task;
+    }
+
+    ctx = task->ctx;
+    wev = c->write;
+
+    if (task->event.complete) {
+        task->event.complete = 0;
+
+        if (ctx->err && ctx->err != NGX_EAGAIN) {
+            wev->error = 1;
+            ngx_connection_error(c, ctx->err, "sendfile() failed");
+            return NGX_ERROR;
+        }
+
+        *sent = ctx->sent;
+
+        return (ctx->sent == ctx->size) ? NGX_DONE : NGX_AGAIN;
+    }
+
+    ctx->file = file;
+    ctx->socket = c->fd;
+    ctx->size = size;
+
+    if (wev->active) {
+        flags = (ngx_event_flags & NGX_USE_CLEAR_EVENT) ? NGX_CLEAR_EVENT
+                                                        : NGX_LEVEL_EVENT;
+
+        if (ngx_del_event(wev, NGX_WRITE_EVENT, flags) == NGX_ERROR) {
+            return NGX_ERROR;
+        }
+    }
+
+    if (file->file->thread_handler(task, file->file) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    *sent = 0;
+
+    return NGX_OK;
+}
+
+
+static void
+ngx_linux_sendfile_thread_handler(void *data, ngx_log_t *log)
+{
+    ngx_linux_sendfile_ctx_t *ctx = data;
+
+    off_t       offset;
+    ssize_t     n;
+    ngx_buf_t  *file;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_CORE, log, 0, "linux sendfile thread handler");
+
+    file = ctx->file;
+    offset = file->file_pos;
+
+again:
+
+    n = sendfile(ctx->socket, file->file->fd, &offset, ctx->size);
+
+    if (n == -1) {
+        ctx->err = ngx_errno;
+
+    } else {
+        ctx->sent = n;
+        ctx->err = 0;
+    }
+
+#if 0
+    ngx_time_update();
+#endif
+
+    ngx_log_debug4(NGX_LOG_DEBUG_EVENT, log, 0,
+                   "sendfile: %z (err: %i) of %uz @%O",
+                   n, ctx->err, ctx->size, file->file_pos);
+
+    if (ctx->err == NGX_EINTR) {
+        goto again;
+    }
+}
+
+#endif /* NGX_THREADS */