Date: Sat, 22 Feb 2020 14:14:53 -0500 From: Pedro Giffuni <pfg@FreeBSD.org> To: Kyle Evans <kevans@freebsd.org>, Li-Wen Hsu <lwhsu@freebsd.org> Cc: Antoine Brodin <antoine@freebsd.org>, Hiroki Sato <hrs@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org> Subject: Re: svn commit: r358152 - head/bin/sh Message-ID: <6f2029df-e08b-65eb-fa28-ca4dcdd351c8@FreeBSD.org> In-Reply-To: <CACNAnaGFqOu9qL6p7pKt7FdMQVGsi6dNs%2BiKg1huet27kacCEw@mail.gmail.com> References: <202002200301.01K31RTk043426@repo.freebsd.org> <CAALwa8kNAb0ME7v6gqdUPCcc%2BnZ9si0VYk0AveEndmTQfxsQ2g@mail.gmail.com> <CAKBkRUzv%2BkB5W-VBacSp4k6YqWyDyCEKZr1W5vEtajojnAMs9A@mail.gmail.com> <CACNAnaGFqOu9qL6p7pKt7FdMQVGsi6dNs%2BiKg1huet27kacCEw@mail.gmail.com>
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For the record ... On 21/02/2020 22:31, Kyle Evans wrote: > On Fri, Feb 21, 2020 at 3:53 PM Li-Wen Hsu <lwhsu@freebsd.org> wrote: >> On Sat, Feb 22, 2020 at 4:58 AM Antoine Brodin <antoine@freebsd.org> wrote: >>> On Thu, Feb 20, 2020 at 4:01 AM Hiroki Sato <hrs@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, This is an example case of why it is important to keep the i386 port building and running. If we don't have a 32 bit port that is easy to build and test many bugs like these can easily go through. Cheers, Pedro.
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