Re: [PATCH 5.1] zread: read files in 4k chunks

From	L A Walsh <bash@tlinx.org>
Newsgroups	gnu.bash.bug
Subject	Re: [PATCH 5.1] zread: read files in 4k chunks
Date	2020-06-23 12:29 -0700
Message-ID	<mailman.342.1592940601.2574.bug-bash@gnu.org> (permalink)
References	<20200622055328.155106-1-Jason@zx2c4.com> <3cac1f66-697d-396d-3dc8-fc5b621638a4@case.edu> <271ebec9-fe1f-7823-a236-2e734657a279@iki.fi> <CAHmME9oLN4OiPnthUi1rdRhwkSPchGcyYRdpEyXz4ciU_cBg0Q@mail.gmail.com> <CALOnQv4rX7qQH7HQLH_dA6bAxSh+8KongB_ba0oWNjG=qUDEJQ@mail.gmail.com>

Show all headers | View raw

The 'stat(2)' system call returns an optimal i/o size for files since some
files in addition to being on disks with a 4k sector size (making 128bytes
a slow choice for reads, and a real slow choice for writes), also can be on
a RAID with it's own optimal i/o size.

I think the 'stat(1)' prog shows the same value with "%o": "stat -c%o" .
65536


On Mon, Jun 22, 2020 at 1:19 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:

> On Mon, Jun 22, 2020 at 2:16 PM Ilkka Virta <itvirta@iki.fi> wrote:
> >
> > On 22.6. 19.35, Chet Ramey wrote:
> > > On 6/22/20 1:53 AM, Jason A. Donenfeld wrote:
> > >> Currently a static sized buffer is used for reading files. At the
> moment
> > >> it is extremely small, making parsing of large files extremely slow.
> > >> Increase this to 4k for improved performance.
> > >
> > > I bumped it up to 1024 initially for testing.
> >
> > It always struck me as odd that Bash used such a small read of 128
> > bytes. Most of the GNU utils I've looked at on Debian use 8192, and a
> > simple test program seems to indicate glibc's stdio reads 4096 bytes at
> > one read() call.
>
> Plus most other shells people use...
>
>

Back to gnu.bash.bug | Previous | Next | Find similar

Thread

Re: [PATCH 5.1] zread: read files in 4k chunks L A Walsh <bash@tlinx.org> - 2020-06-23 12:29 -0700

csiph-web