On Sat, Feb 22, 2020 at 4:58 AM Antoine Brodin <anto...@freebsd.org> wrote: > > 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)
Could you provide more detail? I'm worried because I didn't see related regression from the recent test results. We may need to add more test against the breakage you mentioned. Thanks, Li-Wen _______________________________________________ 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"
