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Further improvements to cUnbufferedFile

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This commit is contained in:
Klaus Schmidinger 2006-02-05 11:06:47 +01:00
parent b6920cd2d8
commit 204f4a322e
2 changed files with 27 additions and 14 deletions
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4
cutter.c
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@ -4,7 +4,7 @@
* See the main source file 'vdr.c' for copyright information and * See the main source file 'vdr.c' for copyright information and
* how to reach the author. * how to reach the author.
* *
* $Id: cutter.c 1.13 2006/02/04 13:40:20 kls Exp $ * $Id: cutter.c 1.14 2006/02/05 11:06:47 kls Exp $
*/ */
#include "cutter.h" #include "cutter.h"
@ -125,7 +125,6 @@ void cCuttingThread::Action(void)
error = "toFile 1"; error = "toFile 1";
break; break;
} }
toFile->SetReadAhead(MEGABYTE(20));
FileSize = 0; FileSize = 0;
} }
LastIFrame = 0; LastIFrame = 0;
@ -166,7 +165,6 @@ void cCuttingThread::Action(void)
error = "toFile 2"; error = "toFile 2";
break; break;
} }
toFile->SetReadAhead(MEGABYTE(20));
FileSize = 0; FileSize = 0;
} }
} }

37
tools.c
View File

@ -4,7 +4,7 @@
* See the main source file 'vdr.c' for copyright information and * See the main source file 'vdr.c' for copyright information and
* how to reach the author. * how to reach the author.
* *
* $Id: tools.c 1.113 2006/02/04 14:07:30 kls Exp $ * $Id: tools.c 1.114 2006/02/05 11:05:56 kls Exp $
*/ */
#include "tools.h" #include "tools.h"
@ -1133,6 +1133,7 @@ ssize_t cUnbufferedFile::Read(void *Data, size_t Size)
#ifdef USE_FADVISE #ifdef USE_FADVISE
off_t jumped = curpos-lastpos; // nonzero means we're not at the last offset off_t jumped = curpos-lastpos; // nonzero means we're not at the last offset
if ((cachedstart < cachedend) && (curpos < cachedstart || curpos > cachedend)) { if ((cachedstart < cachedend) && (curpos < cachedstart || curpos > cachedend)) {
// current position is outside the cached window -- invalidate it.
FadviseDrop(cachedstart, cachedend-cachedstart); FadviseDrop(cachedstart, cachedend-cachedstart);
cachedstart = curpos; cachedstart = curpos;
cachedend = curpos; cachedend = curpos;
@ -1151,7 +1152,7 @@ ssize_t cUnbufferedFile::Read(void *Data, size_t Size)
// Trigger the readahead IO, but only if we've used at least // Trigger the readahead IO, but only if we've used at least
// 1/2 of the previously requested area. This avoids calling // 1/2 of the previously requested area. This avoids calling
// fadvise() after every read() call. // fadvise() after every read() call.
if (ahead - curpos < (off_t)(readahead - readahead / 2)) { if (ahead - curpos < (off_t)(readahead / 2)) {
posix_fadvise(fd, curpos, readahead, POSIX_FADV_WILLNEED); posix_fadvise(fd, curpos, readahead, POSIX_FADV_WILLNEED);
ahead = curpos + readahead; ahead = curpos + readahead;
cachedend = max(cachedend, ahead); cachedend = max(cachedend, ahead);
@ -1161,15 +1162,17 @@ ssize_t cUnbufferedFile::Read(void *Data, size_t Size)
} }
} }
else else
ahead = curpos; // jumped -> we really don't want any readahead. otherwise eg fast-rewind gets in trouble. ahead = curpos; // jumped -> we really don't want any readahead, otherwise e.g. fast-rewind gets in trouble.
} }
if (cachedstart < cachedend) { if (cachedstart < cachedend) {
if (curpos - cachedstart > READCHUNK * 2) { if (curpos - cachedstart > READCHUNK * 2) {
// current position has moved forward enough, shrink tail window.
FadviseDrop(cachedstart, curpos - READCHUNK - cachedstart); FadviseDrop(cachedstart, curpos - READCHUNK - cachedstart);
cachedstart = curpos - READCHUNK; cachedstart = curpos - READCHUNK;
} }
else if (cachedend > ahead && cachedend - curpos > READCHUNK * 2) { else if (cachedend > ahead && cachedend - curpos > READCHUNK * 2) {
// current position has moved back enough, shrink head window.
FadviseDrop(curpos + READCHUNK, cachedend - curpos + READCHUNK); FadviseDrop(curpos + READCHUNK, cachedend - curpos + READCHUNK);
cachedend = curpos + READCHUNK; cachedend = curpos + READCHUNK;
} }
@ -1193,20 +1196,32 @@ ssize_t cUnbufferedFile::Write(const void *Data, size_t Size)
lastpos = max(lastpos, curpos); lastpos = max(lastpos, curpos);
if (written > WRITE_BUFFER) { if (written > WRITE_BUFFER) {
if (lastpos > begin) { if (lastpos > begin) {
// Now do three things:
// 1) Start writeback of begin..lastpos 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
// 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); off_t headdrop = min(begin, WRITE_BUFFER * 2L);
posix_fadvise(fd, begin - headdrop, lastpos - begin + headdrop, POSIX_FADV_DONTNEED); posix_fadvise(fd, begin - headdrop, lastpos - begin + headdrop, POSIX_FADV_DONTNEED);
} }
begin = lastpos = max(0L, curpos - (KILOBYTE(4) - 1)); begin = lastpos = curpos;
totwritten += written; totwritten += written;
written = 0; written = 0;
// The above fadvise() works when writing slowly (recording), but could // The above fadvise() works when writing slowly (recording), but could
// leave cached data around when writing at a high rate (cutting). // leave cached data around when writing at a high rate, e.g. when cutting,
// Also, it seems in some setups, the above does not trigger any I/O and // because by the time we try to flush the cached pages (above) the data
// the fdatasync() call below has to do all the work (reiserfs with some // can still be dirty - we are faster than the disk I/O.
// kind of write gathering enabled). // So we do another round of flushing, just like above, but at larger
// We add 'readahead' to the threshold in an attempt to increase cutting // intervals -- this should catch any pages that couldn't be released
// speed; it's a tradeoff -- speed vs RAM-used. // earlier.
if (totwritten > MEGABYTE(32) + readahead) { if (totwritten > MEGABYTE(32)) {
// 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..
// Uncomment the next line if you think you need them.
//fdatasync(fd); //fdatasync(fd);
off_t headdrop = min(curpos - totwritten, totwritten * 2L); off_t headdrop = min(curpos - totwritten, totwritten * 2L);
posix_fadvise(fd, curpos - totwritten - headdrop, totwritten + headdrop, POSIX_FADV_DONTNEED); posix_fadvise(fd, curpos - totwritten - headdrop, totwritten + headdrop, POSIX_FADV_DONTNEED);