* Buffer reads in FdSource. Together with write buffering, this
significantly cuts down the number of syscalls (e.g., for "nix-store -qR /var/run/current-system" via the daemon, it reduced the number of syscalls in the client from 29134 to 4766 and in the daemon from 44266 to 20666).
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parent
3a48282b06
commit
a3e0656cbb
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@ -2,6 +2,7 @@
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#include "util.hh"
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#include <cstring>
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#include <cerrno>
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namespace nix {
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@ -38,7 +39,28 @@ void FdSink::flush()
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void FdSource::operator () (unsigned char * data, unsigned int len)
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{
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readFull(fd, data, len);
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if (!buffer) buffer = new unsigned char[bufSize];
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while (len) {
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if (!bufPosIn) {
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/* Read as much data as is available (up to the buffer
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size). */
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checkInterrupt();
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ssize_t n = read(fd, (char *) buffer, bufSize);
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if (n == -1) {
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if (errno == EINTR) continue;
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throw SysError("reading from file");
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}
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if (n == 0) throw EndOfFile("unexpected end-of-file");
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bufPosIn = n;
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}
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/* Copy out the data in the buffer. */
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size_t n = len > bufPosIn - bufPosOut ? bufPosIn - bufPosOut : len;
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memcpy(data, buffer + bufPosOut, n);
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data += n; bufPosOut += n; len -= n;
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if (bufPosIn == bufPosOut) bufPosIn = bufPosOut = 0;
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}
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}
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@ -38,9 +38,7 @@ struct FdSink : Sink
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FdSink() : fd(-1), bufSize(32 * 1024), bufPos(0), buffer(0) { }
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FdSink(int fd, unsigned int bufSize = 32 * 1024)
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: fd(fd), bufSize(bufSize), bufPos(0), buffer(0)
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{
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}
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: fd(fd), bufSize(bufSize), bufPos(0), buffer(0) { }
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~FdSink()
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{
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@ -58,15 +56,17 @@ struct FdSink : Sink
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struct FdSource : Source
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{
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int fd;
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unsigned int bufSize, bufPosIn, bufPosOut;
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unsigned char * buffer;
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FdSource()
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{
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fd = -1;
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}
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FdSource() : fd(-1), bufSize(32 * 1024), bufPosIn(0), bufPosOut(0), buffer(0) { }
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FdSource(int fd)
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FdSource(int fd, unsigned int bufSize = 32 * 1024)
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: fd(fd), bufSize(bufSize), bufPosIn(0), bufPosOut(0), buffer(0) { }
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~FdSource()
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{
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this->fd = fd;
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if (buffer) delete[] buffer;
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}
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void operator () (unsigned char * data, unsigned int len);
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