From: Andre Noll <maan@systemlinux.org>
Date: Mon, 24 Oct 2011 13:31:31 +0000 (+0200)
Subject: Merge branch 't/map_populate'
X-Git-Tag: v0.4.9~15
X-Git-Url: http://git.tuebingen.mpg.de/?a=commitdiff_plain;h=a5ad3d4c598bafe28e90e5b623e0a754d6e973d5;hp=-c;p=paraslash.git

Merge branch 't/map_populate'
---

a5ad3d4c598bafe28e90e5b623e0a754d6e973d5
diff --combined NEWS
index 6db72253,50f9b699..3a702729
--- a/NEWS
+++ b/NEWS
@@@ -2,14 -2,6 +2,16 @@@
  0.4.9 (to be announced) "hybrid causality"
  ------------------------------------------
  
 +	- Fix for an endless loop in the mp3 decoder for certain
 +	  (corrupt) mp3 files.
 +	- autogen.sh now detects a distcc setup and adjusts the
 +	  parameter for the -j option of make accordingly.
 +	- Shared memory areas are no longer restricted to 64K. We now
 +	  detect the maximal size of a shared memory area at runtime.
 +	- cleanup of the internal uptime API.
++	- para_server prefaults the mmapped audio file to avoid
++	  delays on slow media.
 +
  --------------------------------------
  0.4.8 (2011-08-19) "nested assignment"
  --------------------------------------
diff --combined vss.c
index f6da52dd,e833543e..e336a9e7
--- a/vss.c
+++ b/vss.c
@@@ -132,7 -132,6 +132,7 @@@ struct fec_group 
  	uint16_t slice_bytes;
  };
  
 +/** A FEC client is always in one of these states. */
  enum fec_client_state {
  	FEC_STATE_NONE = 0,	/**< not initialized and not enabled */
  	FEC_STATE_DISABLED,	/**< temporarily disabled */
@@@ -953,6 -952,10 +953,10 @@@ static int recv_afs_msg(int afs_socket
  	return 1;
  }
  
+ #ifndef MAP_POPULATE
+ #define MAP_POPULATE 0
+ #endif
+ 
  static void recv_afs_result(struct vss_task *vsst, fd_set *rfds)
  {
  	int ret, passed_fd, shmid;
@@@ -987,8 -990,8 +991,8 @@@
  	}
  	mmd->size = statbuf.st_size;
  	mmd->mtime = statbuf.st_mtime;
- 	ret = para_mmap(mmd->size, PROT_READ, MAP_PRIVATE, passed_fd,
- 		0, &vsst->map);
+ 	ret = para_mmap(mmd->size, PROT_READ, MAP_PRIVATE | MAP_POPULATE,
+ 		passed_fd, 0, &vsst->map);
  	if (ret < 0)
  		goto err;
  	close(passed_fd);
@@@ -1077,6 -1080,23 +1081,23 @@@ static void vss_send(struct vss_task *v
  		}
  		mmd->chunks_sent++;
  		mmd->current_chunk++;
+ 		/*
+ 		 * Prefault next chunk(s)
+ 		 *
+ 		 * If the backing device of the memory-mapped audio file is
+ 		 * slow and read-ahead is turned off or prevented for some
+ 		 * reason, e.g. due to memory pressure, it may take much longer
+ 		 * than the chunk interval to get the next chunk on the wire,
+ 		 * causing buffer underruns on the client side. Mapping the
+ 		 * file with MAP_POPULATE seems to help a bit, but it does not
+ 		 * eliminate the delays completely. Moreover, it is supported
+ 		 * only on Linux. So we do our own read-ahead here.
+ 		 */
+ 		buf += len;
+ 		for (i = 0; i < 5 && buf < vsst->map + mmd->size; i++) {
+ 			__a_unused volatile char x = *buf;
+ 			buf += 4096;
+ 		}
  	}
  }