On Thu, Feb 20, 2020 at 4:01 AM Hiroki Sato <h...@freebsd.org> wrote: > > Author: hrs > Date: Thu Feb 20 03:01:27 2020 > New Revision: 358152 > URL: https://svnweb.freebsd.org/changeset/base/358152 > > Log: > Improve performance of "read" built-in command when using a seekable > fd. > > The read built-in command calls read(2) with a 1-byte buffer because > newline characters need to be detected even on a byte stream which > comes from a non-seekable file descriptor. Because of this, the > following script calls >6,000 read(2) to show a 6KiB file: > > while read IN; do echo "$IN"; done < /COPYRIGHT > > When the input byte stream is seekable, it is possible to read a data > block and then reposition the file pointer to where a newline > character found. This change adds a small buffer to do this and > reduces the number of read(2) calls. > > Theoretically, multiple built-in commands reading the same seekable > byte stream in a single pipe chain can share the buffer. However, > this change just makes a single invocation of the read built-in > allocate a buffer and deallocate it every time for simplicity. > Although this causes read(2) to read the same regions multiple times, > the performance penalty should be small compared to the reduction of > read(2) calls. > > Reviewed by: jilles > MFC after: 1 week > Differential Revision: https://reviews.freebsd.org/D23747
This seems to be broken on at least i386. Please either fix or revert. Antoine (with hat: portmgr) _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
