Alexw wrote:
Sometimes the player stops in the middle of a recording due to a zero size request. Here is the log:
vdr: [3836] dvbplayer thread started (pid=3643, tid=3836)
vdr: [3836] resuming replay at index 1950 (0:01:18.01)
vdr: [3837] non blocking file reader thread started (pid=3643, tid=3837)
vdr: [3836] SetBrokenLink: no GOP header found in video packet
vdr: [3836] setting audio track to 1 (0)
vdr: [3836] playing '/var/vdr/video/SERVER/recording/2008-03-28.18.58.50.50.rec/001.vdr'
<<<unexpect stop of replay>>>
vdr: [3837] non blocking file reader thread ended (pid=3643, tid=3837)
vdr: [3836] dvbplayer thread ended (pid=3643, tid=3836)
vdr: [5618] WANT: fd: 25 1068536495 .. 1068722913 SIZE: 186418
vdr: [5618] READ: fd: 25 1068536495 .. 1068666704 SIZE: 130209 jump: 0 ra: 12582912
vdr: [5618] WANT: fd: 25 1068666704 .. 1068983331 SIZE: 316627
vdr: [5618] READ: fd: 25 1068666704 .. 1068680058 SIZE: 13354 jump: 0 ra: 12582912
vdr: [5618] READ: fd: 25 1068680058 .. 1068690344 SIZE: 10286 jump: 0 ra: 12582912
vdr: [5618] READ: fd: 25 1068690344 .. 1068721839 SIZE: 31495 jump: 0 ra: 12582912
vdr: [5618] READ: fd: 25 1068721839 .. 1069246127 SIZE: 524288 jump: 0 ra: 12582912
vdr: [5618] WANT: fd: 25 1069246127 .. 1070294703 SIZE: 1048576
vdr: [5618] READ: fd: 25 1069246127 .. 1069246127 SIZE: 0 jump: 0 ra: 12582912
vdr: [5618] non blocking file reader thread ended (pid=5563, tid=5618)
vdr: [5617] dvbplayer thread ended (pid=5563, tid=5617)
Weird, cUnbufferedFile::Read(Size=0). I'll try to reproduce this.
Sometimes it take a long time to occur, sometimes not.
Did this start after applying my patch, or did it happen in the past too?
Does it always happen at a certain position? Specific stream or bitrate?
I don't recall ever having a similar problem, the number 524288 looks a bit
suspicious...
As you can see the requested size is increasing until it reaches the max buf. This is also a period with freezes in the video (late delivery).
Do these problems (0-sized reads) occur only near the end of a program being recorded?
No, you can experience a stop in the middle of a recording.
Also, I see from the above that the readahead code needs to be more aggressive:
vdr: [5627] WANT: fd: 25 1188531493 .. 1188861741 SIZE: 330248
[... small reads...]
vdr: [5627] READ: fd: 25 1188616808 .. 1189141096 SIZE: 524288 jump: 0 ra: 12582912
the readahead window does not cover the area which is being read later -- this certainly
is likely to stall playback. I'll fix this (i did not expect such a large difference in
read request sizes.)
The attached patch makes the readahead window grow much faster, this will cause more
I/O at the start of playback, but should handle cases like the one above better.
If it works correctly all the ranges mentioned in "READ:" lines should be inside
the preceding "WANT:" range and the playback shouldn't stall.
Here the readahead window grows to ~5Mbytes just after starting playback,
i still need to check that this is not too fast, doesn't saturate the disk and/or
link and cause delays when jumping etc. Tested by playing a few files from an
NFS mount, didn't notice any problems so far.
An incremental patch would look like this (the attached one (vs 1.4.7) already includes it):
diff --git a/tools.c b/tools.c
index a14f799..e22614f 100644
--- a/tools.c
+++ b/tools.c
@@ -1186,13 +1186,13 @@ ssize_t cUnbufferedFile::Read(void *Data, size_t Size)
// Trigger the readahead IO, but only if we've used at least some of the previously
// requested area. This avoids calling fadvise() after every read() call.
size_t cachedsize = cachedend - curpos;
- size_t ra = cachedsize + Size*2 + (size_t)jumped*1;
+ size_t ra = cachedsize + Size*8 + (size_t)jumped*1;
if (cutting)
ra += KILOBYTE(64);
ra = min(readahead, ra);
// Start I/O if we A) used some of the data or B) can read sufficiently large new chunk.
// (A) is important when starting w/ a small readahead.
- if (cachedsize < (ra-ra/4) || cachedsize+KILOBYTE(256) <= ra)
+ if (cachedsize < (ra-ra/16) || cachedsize+KILOBYTE(256) <= ra)
FadviseRead(curpos, ra);
}
else if (jumped >= 0) { // either large forward jump, or FF (jumps by ~4xSize)
artur
diff --git a/cutter.c b/cutter.c
index 5170ae4..7e2e506 100644
--- a/cutter.c
+++ b/cutter.c
@@ -66,7 +66,8 @@ void cCuttingThread::Action(void)
toFile = toFileName->Open();
if (!fromFile || !toFile)
return;
- fromFile->SetReadAhead(MEGABYTE(20));
+ fromFile->CuttingSrc();
+ toFile->CuttingDst();
int Index = Mark->position;
Mark = fromMarks.Next(Mark);
int FileSize = 0;
@@ -91,7 +92,7 @@ void cCuttingThread::Action(void)
if (fromIndex->Get(Index++, &FileNumber, &FileOffset, &PictureType, &Length)) {
if (FileNumber != CurrentFileNumber) {
fromFile = fromFileName->SetOffset(FileNumber, FileOffset);
- fromFile->SetReadAhead(MEGABYTE(20));
+ fromFile->CuttingSrc();
CurrentFileNumber = FileNumber;
}
if (fromFile) {
@@ -124,6 +125,7 @@ void cCuttingThread::Action(void)
error = "toFile 1";
break;
}
+ toFile->CuttingDst();
FileSize = 0;
}
LastIFrame = 0;
@@ -164,6 +166,7 @@ void cCuttingThread::Action(void)
error = "toFile 2";
break;
}
+ toFile->CuttingDst();
FileSize = 0;
}
}
diff --git a/tools.c b/tools.c
index 255c806..e22614f 100644
--- a/tools.c
+++ b/tools.c
@@ -1055,7 +1055,8 @@ bool cSafeFile::Close(void)
#define USE_FADVISE
-#define WRITE_BUFFER KILOBYTE(800)
+//#define dfsyslog dsyslog // uncomment to turn on fadvise related logging
+#define dfsyslog(a...) do {} while (0)
cUnbufferedFile::cUnbufferedFile(void)
{
@@ -1073,12 +1074,19 @@ int cUnbufferedFile::Open(const char *FileName, int Flags, mode_t Mode)
fd = open(FileName, Flags, Mode);
curpos = 0;
#ifdef USE_FADVISE
- begin = lastpos = ahead = 0;
- cachedstart = 0;
- cachedend = 0;
- readahead = KILOBYTE(128);
+ lastpos = 0;
+ lastjump = 0;
+ cachedstart = cachedend = 0;
+ // 4M readahead seems to work for playback while cutting,
+ // but isn't quite enough for FF while cutting...
+ readahead = MEGABYTE(12);
+ writebuffer = KILOBYTE(2000);
written = 0;
totwritten = 0;
+ cutting = 0;
+
+ wbuf = NULL;
+
if (fd >= 0)
posix_fadvise(fd, 0, 0, POSIX_FADV_RANDOM); // we could use POSIX_FADV_SEQUENTIAL, but we do our own readahead, disabling the kernel one.
#endif
@@ -1087,6 +1095,11 @@ int cUnbufferedFile::Open(const char *FileName, int Flags, mode_t Mode)
int cUnbufferedFile::Close(void)
{
+ if (fd >= 0 && wbuf) {
+ if (wbuf_len)
+ WriteBuf(wbuf, wbuf_len);
+ free(wbuf);
+ }
#ifdef USE_FADVISE
if (fd >= 0) {
if (totwritten) // if we wrote anything make sure the data has hit the disk before
@@ -1107,15 +1120,35 @@ int cUnbufferedFile::Close(void)
#define FADVGRAN KILOBYTE(4) // AKA fadvise-chunk-size; PAGE_SIZE or getpagesize(2) would also work.
#define READCHUNK MEGABYTE(8)
-void cUnbufferedFile::SetReadAhead(size_t ra)
+void cUnbufferedFile::CuttingSrc(void)
+{
+ readahead = MEGABYTE(20);
+ cutting = 1;
+}
+
+void cUnbufferedFile::CuttingDst(void)
{
- readahead = ra;
+ writebuffer = MEGABYTE(16); // 4M is too little.
+ cutting = 2;
}
int cUnbufferedFile::FadviseDrop(off_t Offset, off_t Len)
{
- // rounding up the window to make sure that not PAGE_SIZE-aligned data gets freed.
- return posix_fadvise(fd, Offset - (FADVGRAN - 1), Len + (FADVGRAN - 1) * 2, POSIX_FADV_DONTNEED);
+ // Round up the window to make sure that not PAGE_SIZE-aligned data gets freed.
+ // Note that that also means calling this with Len==0 isn't special (unlike fadvise).
+ dfsyslog("DROP: fd:%3d %9zd .. %9zd SIZE: %6zd", fd, Offset, Offset+Len, Len);
+ off_t prewin = min(Offset ,(off_t)FADVGRAN - 1); // must not wrap below 0.
+ return posix_fadvise(fd, Offset - prewin, Len + prewin + (FADVGRAN - 1), POSIX_FADV_DONTNEED);
+}
+
+// Trigger background readahead on the specified range and add
+// it to the "cached" area so that we can drop the data later.
+int cUnbufferedFile::FadviseRead(off_t Offset, off_t Len)
+{
+ dfsyslog("WANT: fd:%3d %9zd .. %9zd SIZE: %6zd", fd, Offset, Offset+Len, Len);
+ cachedstart = min(cachedstart, Offset);
+ cachedend = max(cachedend, Offset+Len);
+ return posix_fadvise(fd, Offset, Len, POSIX_FADV_WILLNEED);
}
off_t cUnbufferedFile::Seek(off_t Offset, int Whence)
@@ -1131,82 +1164,107 @@ ssize_t cUnbufferedFile::Read(void *Data, size_t Size)
if (fd >= 0) {
#ifdef USE_FADVISE
off_t jumped = curpos-lastpos; // nonzero means we're not at the last offset
- if ((cachedstart < cachedend) && (curpos < cachedstart || curpos > cachedend)) {
+
+ dfsyslog("READ: fd:%3d %9zd .. %9zd SIZE: %6zd jump: %9zd ra: %7zd", fd, curpos, curpos+Size, Size, jumped, readahead);
+
+ if (curpos < cachedstart || curpos > cachedend) {
// current position is outside the cached window -- invalidate it.
- FadviseDrop(cachedstart, cachedend-cachedstart);
+ if (cachedstart != cachedend)
+ FadviseDrop(cachedstart, cachedend-cachedstart);
cachedstart = curpos;
cachedend = curpos;
}
- cachedstart = min(cachedstart, curpos);
#endif
ssize_t bytesRead = safe_read(fd, Data, Size);
#ifdef USE_FADVISE
if (bytesRead > 0) {
+ cachedstart = min(cachedstart, curpos);
curpos += bytesRead;
- cachedend = max(cachedend, curpos);
-
// Read ahead:
- // no jump? (allow small forward jump still inside readahead window).
- if (jumped >= 0 && jumped <= (off_t)readahead) {
- // Trigger the readahead IO, but only if we've used at least
- // 1/2 of the previously requested area. This avoids calling
- // fadvise() after every read() call.
- if (ahead - curpos < (off_t)(readahead / 2)) {
- posix_fadvise(fd, curpos, readahead, POSIX_FADV_WILLNEED);
- ahead = curpos + readahead;
- cachedend = max(cachedend, ahead);
- }
- if (readahead < Size * 32) { // automagically tune readahead size.
- readahead = Size * 32;
+ // no jump or small forward jump still inside readahead window.
+ if (jumped >= 0 && curpos <= cachedend) {
+ // Trigger the readahead IO, but only if we've used at least some of the previously
+ // requested area. This avoids calling fadvise() after every read() call.
+ size_t cachedsize = cachedend - curpos;
+ size_t ra = cachedsize + Size*8 + (size_t)jumped*1;
+ if (cutting)
+ ra += KILOBYTE(64);
+ ra = min(readahead, ra);
+ // Start I/O if we A) used some of the data or B) can read sufficiently large new chunk.
+ // (A) is important when starting w/ a small readahead.
+ if (cachedsize < (ra-ra/16) || cachedsize+KILOBYTE(256) <= ra)
+ FadviseRead(curpos, ra);
+ }
+ else if (jumped >= 0) { // either large forward jump, or FF (jumps by ~4xSize)
+ FadviseRead(curpos, ((size_t)jumped < Size*8)?(jumped+Size)*2:Size*2);
+ }
+ else /*if (jumped < 0)*/ { // backward jump:
+ // We don't want any readahead, otherwise e.g. fast-rewind gets in trouble.
+#if 1
+ // But we'll do some read behind for sequential short backward jumps.
+ size_t rbsize = -jumped * 4;
+ if (lastjump <= 0 && (size_t)-jumped < Size * 16 && (size_t)((curpos-Size) - cachedstart ) < rbsize) {
+ // current position has moved back enough, grow tail window.
+ off_t start = max((off_t)0, (off_t)((curpos - Size) - rbsize));
+ FadviseRead(start, rbsize);
}
+#endif
+ // We could reduce readahead window here. But this would lead to already
+ // prefetched data being thrown out by the code below; not exactly ideal
+ // if this jump was only caused by a play mode transition etc.
+ //readahead = Size * 8;
}
- else
- ahead = curpos; // jumped -> we really don't want any readahead, otherwise e.g. fast-rewind gets in trouble.
+ cachedend = max(cachedend, curpos);
}
if (cachedstart < cachedend) {
- if (curpos - cachedstart > READCHUNK * 2) {
+ off_t maxtail = cutting ? KILOBYTE(64) : READCHUNK;
+ off_t maxhead = max(readahead, (size_t)READCHUNK);
+ if (jumped >= 0 && curpos - cachedstart >= maxtail * 2) {
// current position has moved forward enough, shrink tail window.
- FadviseDrop(cachedstart, curpos - READCHUNK - cachedstart);
- cachedstart = curpos - READCHUNK;
+ FadviseDrop(cachedstart, (curpos - maxtail) - cachedstart);
+ cachedstart = curpos - maxtail;
}
- else if (cachedend > ahead && cachedend - curpos > READCHUNK * 2) {
+ else if (jumped < 0 && lastjump < 0 && cachedend - curpos >= maxhead * 2) {
// current position has moved back enough, shrink head window.
- FadviseDrop(curpos + READCHUNK, cachedend - (curpos + READCHUNK));
- cachedend = curpos + READCHUNK;
+ // (a large readahead value may prevent this)
+ FadviseDrop(curpos + maxhead, cachedend - (curpos + maxhead));
+ cachedend = curpos + maxhead;
}
}
lastpos = curpos;
+ lastjump = jumped;
#endif
return bytesRead;
}
return -1;
}
-ssize_t cUnbufferedFile::Write(const void *Data, size_t Size)
+ssize_t cUnbufferedFile::WriteBuf(const void *Data, size_t Size)
{
if (fd >=0) {
ssize_t bytesWritten = safe_write(fd, Data, Size);
+ //dsyslog("WRIT: fd:%3d %9zd .. %9zd SIZE: %6zd", fd, curpos, curpos+Size, Size);
#ifdef USE_FADVISE
if (bytesWritten > 0) {
- begin = min(begin, curpos);
+ cachedstart = min(cachedstart, curpos);
curpos += bytesWritten;
written += bytesWritten;
- lastpos = max(lastpos, curpos);
- if (written > WRITE_BUFFER) {
- if (lastpos > begin) {
+ cachedend = max(cachedend, curpos);
+ if (written > writebuffer) {
+ if (cachedend > cachedstart) {
// Now do three things:
- // 1) Start writeback of begin..lastpos range
+ // 1) Start writeback of cachedstart..cachedend range
// 2) Drop the already written range (by the previous fadvise call)
// 3) Handle nonpagealigned data.
- // This is why we double the WRITE_BUFFER; the first time around the
+ // This is why we double the writebuffer; the first time around the
// last (partial) page might be skipped, writeback will start only after
// second call; the third call will still include this page and finally
// drop it from cache.
- off_t headdrop = min(begin, WRITE_BUFFER * 2L);
- posix_fadvise(fd, begin - headdrop, lastpos - begin + headdrop, POSIX_FADV_DONTNEED);
+ off_t headdrop = min(cachedstart, (off_t)writebuffer * 2);
+ posix_fadvise(fd, cachedstart - headdrop, cachedend - cachedstart + headdrop, POSIX_FADV_DONTNEED);
}
- begin = lastpos = curpos;
+ cachedstart = cachedend = curpos;
totwritten += written;
written = 0;
// The above fadvise() works when writing slowly (recording), but could
@@ -1216,7 +1274,7 @@ ssize_t cUnbufferedFile::Write(const void *Data, size_t Size)
// So we do another round of flushing, just like above, but at larger
// intervals -- this should catch any pages that couldn't be released
// earlier.
- if (totwritten > MEGABYTE(32)) {
+ if (totwritten > MEGABYTE(32) + writebuffer ) {
// It seems in some setups, fadvise() does not trigger any I/O and
// a fdatasync() call would be required do all the work (reiserfs with some
// kind of write gathering enabled), but the syncs cause (io) load..
@@ -1234,6 +1292,26 @@ ssize_t cUnbufferedFile::Write(const void *Data, size_t Size)
return -1;
}
+ssize_t cUnbufferedFile::Write(const void *Data, size_t Size)
+{
+ if (!wbuf) {
+ wbuf_chunk = cutting?MEGABYTE(8):MEGABYTE(4);
+ wbuf = MALLOC(uchar,wbuf_chunk);
+ if (!wbuf)
+ return WriteBuf(Data, Size);
+ wbuf_len = 0;
+ }
+ if (Size <= wbuf_chunk-wbuf_len) {
+ memcpy(wbuf+wbuf_len, Data, Size);
+ wbuf_len += Size;
+ } else {
+ WriteBuf(wbuf, wbuf_len);
+ memcpy(wbuf, Data, Size);
+ wbuf_len = Size;
+ }
+ return Size;
+}
+
cUnbufferedFile *cUnbufferedFile::Create(const char *FileName, int Flags, mode_t Mode)
{
cUnbufferedFile *File = new cUnbufferedFile;
diff --git a/tools.h b/tools.h
index 1f71ec4..ce7283c 100644
--- a/tools.h
+++ b/tools.h
@@ -246,19 +246,26 @@ private:
off_t curpos;
off_t cachedstart;
off_t cachedend;
- off_t begin;
off_t lastpos;
- off_t ahead;
+ off_t lastjump;
size_t readahead;
+ uchar *wbuf;
+ int wbuf_len;
+ int wbuf_chunk;
size_t written;
size_t totwritten;
+ int cutting;
+ size_t writebuffer;
int FadviseDrop(off_t Offset, off_t Len);
+ int FadviseRead(off_t Offset, off_t Len);
+ ssize_t WriteBuf(const void *Data, size_t Size);
public:
cUnbufferedFile(void);
~cUnbufferedFile();
int Open(const char *FileName, int Flags, mode_t Mode = DEFFILEMODE);
int Close(void);
- void SetReadAhead(size_t ra);
+ void CuttingSrc(void);
+ void CuttingDst(void);
off_t Seek(off_t Offset, int Whence);
ssize_t Read(void *Data, size_t Size);
ssize_t Write(const void *Data, size_t Size);
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