On Fri, Feb 21, 2020 at 3:53 PM Li-Wen Hsu <lw...@freebsd.org> wrote: > > 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. >
This trivially failed with the example in the commit message; only the first line would be output. It also triggered a failure of functional_test:read2 in /usr/tests/bin/sh/builtins on i386 (and all of the other platforms with a 32-bit size_t), which would exit with a non-zero status code. I tested and deployed the fix suggested by cem@ as r358235 by just making residue an off_t, Thanks, Kyle Evans _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
