Klaus Schmidinger wrote:
> Artur Skawina wrote:
>> However i consider the whole patch a bugfix :) Now that the fsyncs are
>> disabled it probably isn't that critical though.
>
> So does this mean that without the fdatasync() calls it works ok as
> it is in plain vanilla VDR (without any patch)?
As I haven't run vdr w/o this patch for a long time, i'm not sure. Apparently
things are not ok, as this thread shows, but other vdr-1.3.38+ users with a 2.6
kernel could answer the above question better...
For me it was the sync calls that made me look at this code; w/o them things
weren't as bad, IIRC. I ended up disabling the fdatasyncs completely even when
using fadvise.
> What is the exact meaning of the "WriteStrategy" option?
> Does it simply turn the fadvise stuff on/off, or is there more
> magic behind it? I would prefer a version that works without this
> option, because this is nothing a normal user would easily know
> how to set.
it started as a debugging knob, so i could test the impact of the sync calls,
compare cutting speed w/ fadvise on/off etc.
(Setup.WriteStrategy==1) meant no POSIX_FADV_DONTNEED calls while accessing a
file (the calls were always made when closing a file).
> So, if you can provide a patch against the latest VDR version that
> still uses "#ifdef USE_FADVISE" to completely turn the fadvise
> stuff off, and does _not_ introduce another setup option, I might
> consider including it for the final version 1.4.
i did the minimal fix to the existing vdr code -- note it's far from optimal,
and i suspect there are cases where the fadvise-enabled version isn't
necessarily an improvement. An option which basically turns USE_FADVISE into a
runtime switch would be useful.
As i haven't needed the option myself lately, in fact didn't even remember what
exactly it did and had to check the code, i just killed it, patch attached.
It's vs 1.3.39 because the UI/channel-switch posts scared me away from upgrading
vdr, still remembering the broken menu key experience... ;)
cutter.c part is entirely optional (affects only cutting speed).
artur
-------------- next part --------------
--- vdr-1.3.39.org/cutter.c 2005-10-31 12:26:44.000000000 +0000
+++ vdr-1.3.39/cutter.c 2006-01-28 21:33:39.000000000 +0000
@@ -66,6 +66,8 @@ void cCuttingThread::Action(void)
toFile = toFileName->Open();
if (!fromFile || !toFile)
return;
+ fromFile->SetReadAhead(MEGABYTE(20));
+ toFile->SetReadAhead(MEGABYTE(20));
int Index = Mark->position;
Mark = fromMarks.Next(Mark);
int FileSize = 0;
@@ -90,6 +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));
CurrentFileNumber = FileNumber;
}
if (fromFile) {
@@ -118,10 +121,11 @@ void cCuttingThread::Action(void)
break;
if (FileSize > MEGABYTE(Setup.MaxVideoFileSize)) {
toFile = toFileName->NextFile();
- if (toFile < 0) {
+ if (!toFile) {
error = "toFile 1";
break;
}
+ toFile->SetReadAhead(MEGABYTE(20));
FileSize = 0;
}
LastIFrame = 0;
@@ -158,10 +162,11 @@ void cCuttingThread::Action(void)
cutIn = true;
if (Setup.SplitEditedFiles) {
toFile = toFileName->NextFile();
- if (toFile < 0) {
+ if (!toFile) {
error = "toFile 2";
break;
}
+ toFile->SetReadAhead(MEGABYTE(20));
FileSize = 0;
}
}
--- vdr-1.3.39.org/tools.c 2006-01-15 14:31:45.000000000 +0000
+++ vdr-1.3.39/tools.c 2006-01-28 21:48:22.000000000 +0000
@@ -1040,10 +1040,9 @@ bool cSafeFile::Close(void)
// --- cUnbufferedFile -------------------------------------------------------
-//#define USE_FADVISE
+#define USE_FADVISE
-#define READ_AHEAD MEGABYTE(2)
-#define WRITE_BUFFER MEGABYTE(10)
+#define WRITE_BUFFER KILOBYTE(800)
cUnbufferedFile::cUnbufferedFile(void)
{
@@ -1059,8 +1058,17 @@ int cUnbufferedFile::Open(const char *Fi
{
Close();
fd = open(FileName, Flags, Mode);
- begin = end = ahead = -1;
+ curpos = 0;
+ begin = lastpos = ahead = 0;
+ readahead = 128*1024;
+ pendingreadahead = 0;
written = 0;
+ totwritten = 0;
+ if (fd >= 0) {
+ // we could use POSIX_FADV_SEQUENTIAL, but we do our own readahead
+ // disabling the kernel one.
+ posix_fadvise(fd, 0, 0, POSIX_FADV_RANDOM);
+ }
return fd;
}
@@ -1068,15 +1076,10 @@ int cUnbufferedFile::Close(void)
{
#ifdef USE_FADVISE
if (fd >= 0) {
- if (ahead > end)
- end = ahead;
- if (begin >= 0 && end > begin) {
- //dsyslog("close buffer: %d (flush: %d bytes, %ld-%ld)", fd, written, begin, end);
- if (written)
- fdatasync(fd);
- posix_fadvise(fd, begin, end - begin, POSIX_FADV_DONTNEED);
- }
- begin = end = ahead = -1;
+ 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.
+ posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
+ begin = lastpos = ahead = 0;
written = 0;
}
#endif
@@ -1085,45 +1088,95 @@ int cUnbufferedFile::Close(void)
return close(OldFd);
}
-off_t cUnbufferedFile::Seek(off_t Offset, int Whence)
-{
- if (fd >= 0)
- return lseek(fd, Offset, Whence);
- return -1;
-}
-
+// When replaying and going eg FF->PLAY the position jumps back 2..8M
+// hence we might not want to drop that data at once.
+// Ignoring this for now to avoid making this even more complex,
+// but we could at least try to handle the common cases.
+// (PLAY->FF->PLAY, small jumps, moving editing marks etc)
+
+#define KREADAHEAD MEGABYTE(4) // amount (guess) of kernel/fs prefetch that
+ // could happen in addition to our own.
+#define FADVGRAN 4096 // AKA fadvise-chunk-size; PAGE_SIZE or
+ // getpagesize(2) would also work.
+
ssize_t cUnbufferedFile::Read(void *Data, size_t Size)
{
if (fd >= 0) {
#ifdef USE_FADVISE
- off_t pos = lseek(fd, 0, SEEK_CUR);
- // jump forward - adjust end position
- if (pos > end)
- end = pos;
- // after adjusting end - don't clear more than previously requested
- if (end > ahead)
- end = ahead;
- // jump backward - drop read ahead of previous run
- if (pos < begin)
- end = ahead;
- if (begin >= 0 && end > begin)
- posix_fadvise(fd, begin - KILOBYTE(200), end - begin + KILOBYTE(200), POSIX_FADV_DONTNEED);//XXX macros/parameters???
- begin = pos;
+ off_t jumped = curpos-lastpos; // nonzero means we're not at the last offset
+ if (jumped) { // ie some kind of jump happened.
+ pendingreadahead += ahead-lastpos+KREADAHEAD;
+ // jumped forward? - treat as if we did read all the way to current pos.
+ if (jumped >= 0) {
+ lastpos = curpos;
+ // but clamp at ahead so we don't clear more than previously requested.
+ // (would be mostly harmless anyway, unless we got more than one reader of this file)
+ if (lastpos > (ahead+KREADAHEAD))
+ lastpos = ahead+KREADAHEAD;
+ }
+ // jumped backward? - drop both last read _and_ read-ahead
+ else
+ if (curpos < begin)
+ lastpos = ahead+KREADAHEAD;
+ // jumped backward, but still inside prev read window? - pretend we read less.
+ else /* if (curpos >= begin) */
+ lastpos = curpos;
+ }
+
#endif
ssize_t bytesRead = safe_read(fd, Data, Size);
#ifdef USE_FADVISE
+ // Now drop data accessed during _previous_ Read(). (ie. begin...lastpos)
+ // fadvise() internally has page granularity; it drops only whole pages
+ // from the range we specify (since it cannot know if we will be accessing
+ // the rest). This is why we drop only the previously read data, and do it
+ // _after_ the current read() call, while rounding up the window to make
+ // sure that even not PAGE_SIZE-aligned data gets freed.
+ // We're also trying merge the fadvise calls a bit in order to reduce overhead
+ // (to avoid a fadvise() call here for every read() above).
+ if (begin >= 0 && lastpos > begin)
+ if (jumped || (size_t)(lastpos-begin) > readahead) {
+ //dsyslog("taildrop: %ld..%ld size %ld", begin, lastpos, lastpos-begin);
+ posix_fadvise(fd, begin-(FADVGRAN-1), lastpos-begin+(FADVGRAN-1)*2, POSIX_FADV_DONTNEED);
+ begin = curpos;
+ }
+
if (bytesRead > 0) {
- pos += bytesRead;
- end = pos;
- // this seems to trigger a non blocking read - this
- // may or may not have been finished when we will be called next time.
- // If it is not finished we can't release the not yet filled buffers.
- // So this is commented out till we find a better solution.
- //posix_fadvise(fd, pos, READ_AHEAD, POSIX_FADV_WILLNEED);
- ahead = pos + READ_AHEAD;
+ curpos += bytesRead;
+ //dsyslog("jump: %06ld ra: %06ld size: %ld", jumped, (long)readahead, (long)Size);
+
+ // 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
+ // 1/4 of the previously requested area. This avoids calling
+ // fadvise() after every read() call.
+ if ((ahead-curpos)<(off_t)(readahead-readahead/4)) {
+ posix_fadvise(fd, curpos, readahead, POSIX_FADV_WILLNEED);
+ ahead = curpos + readahead;
+ }
+ if ( readahead < Size*64 ) { // automagically tune readahead size.
+ readahead = Size*64;
+ //dsyslog("Readahead for fd: %d increased to %ld", fd, (long)readahead);
+ }
+ }
+ else {
+ // jumped - we really don't want any readahead now. otherwise
+ // eg fast-rewind gets in trouble.
+ ahead = curpos;
+
+ // Every now and then, flush all cached data from this file; mostly
+ // to get rid of nonflushed readahead coming from _previous_ jumps
+ // (if the readahead I/O hasn't finished by the time we called
+ // fadvice() to undo it, the data could still be cached).
+ // The accounting does not have to be 100% accurate, as long as
+ // this triggers after _some_ jumps we should be ok.
+ if (pendingreadahead>MEGABYTE(40)) {
+ pendingreadahead = 0;
+ posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
+ }
+ }
}
- else
- end = pos;
+ lastpos = curpos;
#endif
return bytesRead;
}
@@ -1132,29 +1185,37 @@ ssize_t cUnbufferedFile::Read(void *Data
ssize_t cUnbufferedFile::Write(const void *Data, size_t Size)
{
+ //dsyslog("Unbuffered:Write: fd: %d %8ld..%8ld size: %5ld", fd, curpos, curpos+Size, (long)Size);
if (fd >=0) {
-#ifdef USE_FADVISE
- off_t pos = lseek(fd, 0, SEEK_CUR);
-#endif
ssize_t bytesWritten = safe_write(fd, Data, Size);
#ifdef USE_FADVISE
- if (bytesWritten >= 0) {
+ if (bytesWritten > 0) {
+ begin = min(begin, curpos);
+ curpos += bytesWritten;
written += bytesWritten;
- if (begin >= 0) {
- if (pos < begin)
- begin = pos;
- }
- else
- begin = pos;
- if (pos + bytesWritten > end)
- end = pos + bytesWritten;
+ lastpos = max(lastpos, curpos);
if (written > WRITE_BUFFER) {
- //dsyslog("flush buffer: %d (%d bytes, %ld-%ld)", fd, written, begin, end);
- fdatasync(fd);
- if (begin >= 0 && end > begin)
- posix_fadvise(fd, begin, end - begin, POSIX_FADV_DONTNEED);
- begin = end = -1;
+ //dsyslog("flush buffer: %d (%d bytes, %ld-%ld)", fd, written, begin, lastpos);
+ if (lastpos>begin) {
+ off_t headdrop = min(begin, WRITE_BUFFER*2L);
+ posix_fadvise(fd, begin-headdrop, lastpos-begin+headdrop, POSIX_FADV_DONTNEED);
+ }
+ begin = lastpos = max(0L, curpos-4095);
+ totwritten += written;
written = 0;
+ // The above fadvise() works when writing slowly (recording), but could
+ // leave cached data around when writing at a high rate (cutting).
+ // Also, it seems in some setups, the above does not trigger any I/O and
+ // the fdatasync() call below has to do all the work (reiserfs with some
+ // kind of write gathering enabled).
+ // We add 'readahead' to the threshold in an attempt to increase cutting
+ // speed; it's a tradeoff -- speed vs RAM-used.
+ if (totwritten>(MEGABYTE(32)+readahead)) {
+ //fdatasync(fd);
+ off_t headdrop = min(curpos-totwritten, totwritten*2L);
+ posix_fadvise(fd, curpos-totwritten-headdrop, totwritten+headdrop, POSIX_FADV_DONTNEED);
+ totwritten = 0;
+ }
}
}
#endif
--- vdr-1.3.39.org/tools.h 2006-01-08 11:40:37.000000000 +0000
+++ vdr-1.3.39/tools.h 2006-01-28 21:32:26.000000000 +0000
@@ -237,22 +237,40 @@ public:
/// cUnbufferedFile is used for large files that are mainly written or read
/// in a streaming manner, and thus should not be cached.
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
class cUnbufferedFile {
private:
int fd;
+ off_t curpos;
off_t begin;
- off_t end;
+ off_t lastpos;
off_t ahead;
- ssize_t written;
+ size_t pendingreadahead;
+ size_t readahead;
+ size_t written;
+ size_t totwritten;
public:
cUnbufferedFile(void);
~cUnbufferedFile();
int Open(const char *FileName, int Flags, mode_t Mode = DEFFILEMODE);
int Close(void);
- off_t Seek(off_t Offset, int Whence);
+ off_t Seek(off_t Offset, int Whence)
+ {
+ //dsyslog("Seek: fd: %d offs: %ld whence: %d diff: %ld", fd, (long)Offset, Whence, Offset-curpos);
+ if (Whence == SEEK_SET && Offset == curpos)
+ return curpos;
+
+ curpos = lseek(fd, Offset, Whence);
+ return curpos;
+ }
+
ssize_t Read(void *Data, size_t Size);
ssize_t Write(const void *Data, size_t Size);
static cUnbufferedFile *Create(const char *FileName, int Flags, mode_t Mode = DEFFILEMODE);
+ void SetReadAhead(size_t ra) { readahead = ra; };
};
class cLockFile {
