Speed up readline() by using a user-space ring buffer

src/calibre/srv/http_request.py

@@ -160,7 +160,7 @@ class HTTPRequest(Connection):
     def read(self, buf, endpos):
         size = endpos - buf.tell()
         if size > 0:
-            data = self.recv(min(size, DEFAULT_BUFFER_SIZE))
+            data = self.recv(size)
             if data:
                 buf.write(data)
                 return len(data) >= size
@@ -170,19 +170,21 @@ class HTTPRequest(Connection):
             return True
 
     def readline(self, buf):
-        if buf.tell() >= self.max_header_line_size - 1:
+        line = self.read_buffer.readline()
+        buf.write(line)
+        if buf.tell() > self.max_header_line_size:
             self.simple_response(self.header_line_too_long_error_code)
             return
-        data = self.recv(1)
-        if data:
-            buf.write(data)
-            if b'\n' == data:
+        if line.endswith(b'\n'):
             line = buf.getvalue()
             buf.seek(0), buf.truncate()
-                if line.endswith(b'\r\n'):
-                    return line
-                else:
+            if not line.endswith(b'\r\n'):
                 self.simple_response(httplib.BAD_REQUEST, 'HTTP requires CRLF line terminators')
+                return
+            return line
+        if not line:
+            # read buffer is empty, fill it
+            self.fill_read_buffer()
 
     def connection_ready(self):
         'Become ready to read an HTTP request'

src/calibre/srv/loop.py

@@ -22,6 +22,89 @@ from calibre.utils.monotonic import monotonic
 
 READ, WRITE, RDWR = 'READ', 'WRITE', 'RDWR'
 
+class ReadBuffer(object):
+
+    __slots__ = ('ba', 'buf', 'read_pos', 'write_pos', 'full_state')
+
+    def __init__(self, size=4096):
+        self.ba = bytearray(size)
+        self.buf = memoryview(self.ba)
+        self.read_pos = 0
+        self.write_pos = 0
+        self.full_state = WRITE
+
+    @property
+    def has_data(self):
+        return self.read_pos != self.write_pos or self.full_state is READ
+
+    @property
+    def has_space(self):
+        return self.read_pos != self.write_pos or self.full_state is WRITE
+
+    def read(self, size):
+        # Read from this buffer, retuning the read bytes as a bytestring
+        if self.read_pos == self.write_pos and self.full_state is WRITE:
+            return b''
+        if self.read_pos < self.write_pos:
+            sz = min(self.write_pos - self.read_pos, size)
+            npos = self.read_pos + sz
+            ans = self.buf[self.read_pos:npos].tobytes()
+            self.read_pos = npos
+            if self.read_pos == self.write_pos:
+                self.full_state = WRITE
+        else:
+            sz = min(size, len(self.buf) - self.read_pos)
+            ans = self.buf[self.read_pos:self.read_pos + sz].tobytes()
+            self.read_pos = (self.read_pos + sz) % len(self.buf)
+            if self.read_pos == self.write_pos:
+                self.full_state = WRITE
+            if size > sz and self.read_pos < self.write_pos:
+                ans += self.read(size - len(ans.buf))
+        return ans
+
+    def recv_from(self, socket):
+        # Write into this buffer from socket, return number of bytes written
+        if self.read_pos == self.write_pos and self.full_state is READ:
+            return 0
+        if self.write_pos < self.read_pos:
+            num = socket.recv_into(self.buf[self.write_pos:self.read_pos])
+            self.write_pos += num
+        else:
+            num = socket.recv_into(self.buf[self.write_pos:])
+            self.write_pos = (self.write_pos + num) % len(self.buf)
+        if self.write_pos == self.read_pos:
+            self.full_state = READ
+        return num
+
+    def readline(self):
+        # Return whatever is in the buffer upto (and including) the first \n
+        if self.read_pos == self.write_pos and self.full_state is WRITE:
+            return b''
+        if self.read_pos < self.write_pos:
+            pos = self.ba.find(b'\n', self.read_pos, self.write_pos)
+            if pos < 0:
+                pos = self.write_pos - 1
+            ans = self.buf[self.read_pos:pos + 1].tobytes()
+            self.read_pos = (pos + 1) % len(self.buf)
+            if self.read_pos == self.write_pos:
+                self.full_state = WRITE
+        else:
+            pos = self.ba.find(b'\n', self.read_pos)
+            if pos < 0:
+                pos = self.ba.find(b'\n', 0, self.write_pos)
+                if pos < 0:
+                    pos = self.write_pos - 1
+                ans = self.buf[self.read_pos:].tobytes() + self.buf[:pos+1].tobytes()
+                self.read_pos = (pos + 1) % len(self.buf)
+                if self.read_pos == self.write_pos:
+                    self.full_state = WRITE
+            else:
+                ans = self.buf[self.read_pos:pos + 1].tobytes()
+                self.read_pos = (pos + 1) % len(self.buf)
+                if self.read_pos == self.write_pos:
+                    self.full_state = WRITE
+        return ans
+
 class Connection(object):
 
     def __init__(self, socket, opts, ssl_context, tdir):
@@ -31,6 +114,7 @@ class Connection(object):
         self.ssl_context = ssl_context
         self.wait_for = READ
         self.response_started = False
+        self.read_buffer = ReadBuffer()
         if self.ssl_context is not None:
             self.ready = False
             self.socket = self.ssl_context.wrap_socket(socket, server_side=True, do_handshake_on_connect=False)
@@ -86,9 +170,15 @@ class Connection(object):
                 return 0
             raise
 
-    def recv(self, buffer_size):
+    def recv(self, amt):
+        # If there is data in the read buffer we have to return only that,
+        # since we dont know if the socket has signalled it is ready for
+        # reading
+        if self.read_buffer.has_data:
+            return self.read_buffer.read(amt)
+        # read buffer is empty, so read directly from socket
         try:
-            data = self.socket.recv(buffer_size)
+            data = self.socket.recv(amt)
             self.last_activity = monotonic()
             if not data:
                 # a closed connection is indicated by signaling
@@ -104,6 +194,22 @@ class Connection(object):
                 return b''
             raise
 
+    def fill_read_buffer(self):
+        try:
+            num = self.read_buffer.recv_from(self.socket)
+            self.last_activity = monotonic()
+            if not num:
+                # a closed connection is indicated by signaling
+                # a read condition, and having recv() return 0.
+                self.ready = False
+        except socket.error as e:
+            if e.errno in socket_errors_nonblocking or e.errno in socket_errors_eintr:
+                return
+            if e.errno in socket_errors_socket_closed:
+                self.ready = False
+                return
+            raise
+
     def close(self):
         self.ready = False
         self.handle_event = None  # prevent reference cycles
@@ -262,8 +368,19 @@ class ServerLoop(object):
                     self.log.debug('Closing connection because of extended inactivity')
                     self.close(s, conn)
 
-        read_needed = [c.socket for c in self.connection_map.itervalues() if c.wait_for is READ or c.wait_for is RDWR]
-        write_needed = [c.socket for c in self.connection_map.itervalues() if c.wait_for is WRITE or c.wait_for is RDWR]
+        read_needed, write_needed, readable = [], [], []
+        for c in self.connection_map.itervalues():
+            if c.wait_for is READ:
+                (readable if c.read_buffer.has_data else read_needed).append(c.socket)
+            elif c.wait_for is WRITE:
+                write_needed.append(c.socket)
+            else:
+                write_needed.append(c)
+                (readable if c.read_buffer.has_data else read_needed).append(c.socket)
+
+        if readable:
+            writable = []
+        else:
             try:
                 readable, writable, _ = select.select([self.socket] + read_needed, write_needed, [], self.opts.timeout)
             except select.error as e: