K 10
svn:author
V 7
glebius
K 8
svn:date
V 27
2014-02-12T20:06:26.711696Z
K 7
svn:log
V 938
Make the sendfile(2) call non-blocking on disk I/O, but unlike SF_NODISKIO,
still performing the I/O. The new call is a drop-in replacement for older
sendfile(2), so applications like web-servers do not need to be recompiled
or reconfigured to achieve the benefit.

The mechanics of the change are the following:

o We grab enough pages to fill the socket buffer.
o We iterate through pages, and request I/O on those, that are not
  valid. The I/O is requested via VOP_GETPAGES_ASYNC(), so it doesn't
  block.
o If we did initiated any I/Os, then we send data to the buffer as
  SB_NOTREADY data, since I/Os are still in progress. And return.
o Once the last I/O completes, we mark our data in socket as ready,
  and if we were the blocker of the socket, then we initiate send.

The code still has quite a lot of rough places, but has already been
tested at Netflix with positive results.

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.

END