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* Buffer writes in FdSink. This significantly reduces the number of

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system calls / context switches when dumping a NAR and in the worker
  protocol.
This commit is contained in:
Eelco Dolstra 2011-12-14 23:30:06 +00:00
parent 893cac1402
commit 3a48282b06
4 changed files with 51 additions and 15 deletions
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25
src/libutil/serialise.cc
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@ -9,7 +9,30 @@ namespace nix {
void FdSink::operator () (const unsigned char * data, unsigned int len)
{
writeFull(fd, data, len);
if (!buffer) buffer = new unsigned char[bufSize];
while (len) {
/* Optimisation: bypass the buffer if the data exceeds the
buffer size and there is no unflushed data. */
if (bufPos == 0 && len >= bufSize) {
writeFull(fd, data, len);
break;
}
/* Otherwise, copy the bytes to the buffer. Flush the buffer
when it's full. */
size_t n = bufPos + len > bufSize ? bufSize - bufPos : len;
memcpy(buffer + bufPos, data, n);
data += n; bufPos += n; len -= n;
if (bufPos == bufSize) flush();
}
}
void FdSink::flush()
{
if (fd == -1 || bufPos == 0) return;
writeFull(fd, buffer, bufPos);
bufPos = 0;
}