i suspected the readahead was being too aggressive, hence this -- a more autotuning readahead + general cleanups. I think the only bugfix in here is the one i just sent separately, but this code is from vdr-1.3.45 era, i might have forgotten something. (.46+ kept segfaulting here, found the cause only today -- a missing dependency in the streamdev plugin)
Posting this just in case somebody has trouble w/ the fadvise code and wants to try something else. Commenting out "#define USE_FADVISE_RA" should disable the manual readahead completely, but still flush written data out, preventing an ongoing recording from eating up all free ram etc.
artur
--- vdr-1.3.49.org/cutter.c 2006-02-12 10:07:23.000000000 +0000 +++ vdr-1.3.49/cutter.c 2006-04-29 08:54:19.000000000 +0000 @@ -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; } } --- vdr-1.3.49.org/tools.c 2006-04-21 15:12:47.000000000 +0000 +++ vdr-1.3.49/tools.c 2006-04-29 08:54:19.000000000 +0000 @@ -1060,9 +1060,14 @@ bool cSafeFile::Close(void)
// --- cUnbufferedFile -------------------------------------------------------
-#define USE_FADVISE +#define USE_FADVISE_RA +#define USE_FADVISE_DB
-#define WRITE_BUFFER KILOBYTE(800) +//#define dfsyslog dsyslog // turn on fadvise related logging +#define dfsyslog(a...) do {} while (0) + +#define FADVGRAN KILOBYTE(4) // AKA fadvise-chunk-size; PAGE_SIZE or getpagesize(2) would also work. +#define READCHUNK MEGABYTE(8)
cUnbufferedFile::cUnbufferedFile(void) { @@ -1079,13 +1084,16 @@ int cUnbufferedFile::Open(const char *Fi Close(); fd = open(FileName, Flags, Mode); curpos = 0; -#ifdef USE_FADVISE - begin = lastpos = ahead = 0; - cachedstart = 0; - cachedend = 0; - readahead = KILOBYTE(128); +#if defined(USE_FADVISE_RA) || defined(USE_FADVISE_DB) + lastpos = 0; + lastjump = 0; + cachedstart = cachedend = 0; + //readahead = READCHUNK; + readahead = KILOBYTE(768); + writebuffer = KILOBYTE(800); written = 0; totwritten = 0; + cutting = 0; 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 @@ -1094,7 +1102,7 @@ int cUnbufferedFile::Open(const char *Fi
int cUnbufferedFile::Close(void) { -#ifdef USE_FADVISE +#if defined(USE_FADVISE_DB) if (fd >= 0) { if (totwritten) // if we wrote anything make sure the data has hit the disk before fdatasync(fd); // calling fadvise, as this is our last chance to un-cache it. @@ -1111,18 +1119,35 @@ int cUnbufferedFile::Close(void) // We try to handle the common cases such as PLAY->FF->PLAY, small // jumps, moving editing marks etc.
-#define FADVGRAN KILOBYTE(4) // AKA fadvise-chunk-size; PAGE_SIZE or getpagesize(2) would also work. -#define READCHUNK MEGABYTE(8) +void cUnbufferedFile::CuttingSrc(void) +{ + readahead = MEGABYTE(16); + cutting = 1; +}
-void cUnbufferedFile::SetReadAhead(size_t ra) +void cUnbufferedFile::CuttingDst(void) { - readahead = ra; + writebuffer = MEGABYTE(16); + 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) @@ -1136,54 +1161,78 @@ off_t cUnbufferedFile::Seek(off_t Offset ssize_t cUnbufferedFile::Read(void *Data, size_t Size) { if (fd >= 0) { -#ifdef USE_FADVISE +#ifdef USE_FADVISE_RA 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 +#ifdef USE_FADVISE_RA 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*1 + (size_t)jumped*1; + if (cutting) + ra += KILOBYTE(128); + 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(128) <= 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 0 + // But we'll do some read behind for sequential short backward jumps. + size_t rbsize = -jumped * 16; + if (lastjump < 0 && (size_t)-jumped < Size * 8 && (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 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(32) : 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; } @@ -1194,26 +1243,27 @@ ssize_t cUnbufferedFile::Write(const voi { if (fd >=0) { ssize_t bytesWritten = safe_write(fd, Data, Size); -#ifdef USE_FADVISE + //dsyslog("WRIT: fd:%3d %9zd .. %9zd SIZE: %6zd", fd, curpos, curpos+Size, Size); +#ifdef USE_FADVISE_DB 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 @@ -1223,7 +1273,7 @@ ssize_t cUnbufferedFile::Write(const voi // 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.. --- vdr-1.3.49.org/tools.h 2006-04-16 10:40:45.000000000 +0000 +++ vdr-1.3.49/tools.h 2006-04-29 08:54:19.000000000 +0000 @@ -245,19 +245,22 @@ 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; 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); 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);