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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Thu, 7 Jan 2010 13:31:01 +0000 (UTC)
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Subject: svn commit: r201743 - head/lib/libc/sys
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Author: kib
Date: Thu Jan  7 13:31:00 2010
New Revision: 201743
URL: http://svn.freebsd.org/changeset/base/201743

Log:
  Give some information on SF_MNOWAIT flag.
  
  MFC after:	3 days

Modified:
  head/lib/libc/sys/sendfile.2

Modified: head/lib/libc/sys/sendfile.2
==============================================================================
--- head/lib/libc/sys/sendfile.2	Thu Jan  7 12:58:03 2010	(r201742)
+++ head/lib/libc/sys/sendfile.2	Thu Jan  7 13:31:00 2010	(r201743)
@@ -116,9 +116,17 @@ Busy servers may benefit by transferring
 block to a separate I/O worker thread.
 .It
 .Dv SF_MNOWAIT .
-(description missing)
+Do not wait for some kernel resource to become available,
+in particular,
+.Vt mbuf
+and
+.Vt sf_buf .
+The flag does not make the
+.Fn sendfile
+syscall trully non-blocking, since other resources are still allocated
+in blocking fashion.
 .It
-.Dv SF_SYNC ,
+.Dv SF_SYNC .
 .Nm
 sleeps until the network stack no longer references the VM pages
 of the file, making subsequent modifications to it safe.