Re: [PATCH v4 0/7] kernel tinification: optionally
compile out splice family of syscalls (splice, vmsplice, tee and sendfile)
[Posted December 3, 2014 by corbet]
| From: |
| josh-iaAMLnmF4UmaiuxdJuQwMA-AT-public.gmane.org |
| To: |
| Randy Dunlap <rdunlap-wEGCiKHe2LqWVfeAwA7xHQ-AT-public.gmane.org> |
| Subject: |
| Re: [PATCH v4 0/7] kernel tinification: optionally compile out splice family of syscalls (splice, vmsplice, tee and sendfile) |
| Date: |
| Tue, 25 Nov 2014 11:00:28 -0800 |
| Message-ID: |
| <20141125190028.GB24891@cloud> |
| Cc: |
| "Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA-AT-public.gmane.org>, Trond Myklebust <trond.myklebust-7I+n7zu2hftEKMMhf/gKZA-AT-public.gmane.org>, Bertrand Jacquin <beber-2YnHqweIUXrk1uMJSBkQmQ-AT-public.gmane.org>, Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA-AT-public.gmane.org>, "J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw-AT-public.gmane.org>, Eric Dumazet <edumazet-hpIqsD4AKlfQT0dZR+AlfA-AT-public.gmane.org>, =?utf-8?B?6JSh5q2j6b6Z?= <zhenglong.cai-TJRtMXcVgQTM1kAEIRd3EQ-AT-public.gmane.org>, Jeff Layton <jlayton-vpEMnDpepFuMZCB2o+C8xQ-AT-public.gmane.org>, Tom Herbert <therbert-hpIqsD4AKlfQT0dZR+AlfA-AT-public.gmane.org>, Alexei Starovoitov <ast-uqk4Ao+rVK5Wk0Htik3J/w-AT-public.gmane.org>, Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA-AT-public.gmane.org>, Peter Foley <pefoley2-lY0TAiDIAFlBDgjK7y7TUQ-AT-public.gmane.org>, Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA-AT-public.gmane.org>, Xiao Guangrong <xiaoguangrong-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8-AT-public.gmane.org>, Geert Uytterhoeven <geert-Td1EMuHUCqxL1ZNQvxDV9g-AT-public.gmane.org>, Mel Gorman <mgorman-l3A5Bk7waGM-AT-public.gmane.org>, Matt Turner <mattst88-Re5JQEeQqe8AvxtiuMwx3w-AT-public.gmane.org>, "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8-AT-public.gmane.org>, Alexander Duyck <alexander.h.duyck-ral2JQCrhuEAvxtiuMwx3w-AT-public.gmane.org>, Pieter Smith <pieter-qeJ+1H9vRZbz+pZb47iToQ-AT-public.gmane.org>, "open list:FUSE: FILESYSTEM..." <fuse-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f-AT-public.gmane.org>, "Luis R. Rod |
| Archive‑link: | |
Article |
On Tue, Nov 25, 2014 at 08:17:58AM -0800, Randy Dunlap wrote:
> On 11/24/2014 03:00 PM, Pieter Smith wrote:
> >REPO: https://github.com/smipi1/linux-tinification.git
> >
> >BRANCH: tiny/config-syscall-splice
> >
> >BACKGROUND: This patch-set forms part of the Linux Kernel Tinification effort (
> > https://tiny.wiki.kernel.org/).
> >
> >GOAL: Support compiling out the splice family of syscalls (splice, vmsplice,
> > tee and sendfile) along with all supporting infrastructure if not needed.
> > Many embedded systems will not need the splice-family syscalls. Omitting them
> > saves space.
>
> Hi,
>
> Is the splice family of syscalls the only one that tiny has identified
> for optional building or can we expect similar treatment for other
> syscalls?
Pretty much any system call that you could conceive of writing a
userspace without.
There's a partial project list at https://tiny.wiki.kernel.org/projects.
> Why will many embedded systems not need these syscalls? You know
> exactly what apps they run and you are positive that those apps do
> not use splice?
Yes, precisely. We're talking about embedded systems small enough that
you're booting with init=/your/app and don't even call fork(), where you
know exactly what code you're putting in and what libraries you use.
And they're almost certainly not running glibc.
> >RESULTS: A tinyconfig bloat-o-meter score for the entire patch-set:
> >
> >add/remove: 0/41 grow/shrink: 5/7 up/down: 23/-8422 (-8399)
>
> The summary is that this patch saves around 8 KB of code space --
> is that correct?
Right. For reference, we're talking about kernels where the *total*
size is a few hundred kB.
> How much storage space do embedded systems have nowadays?
For the embedded systems we're targeting for the tinification effort, in
a first pass: 512k-2M of storage (often for an *uncompressed* kernel, to
support execute-in-place), and 128k-512k of memory. We've successfully
built useful kernels and userspaces for such environments, and we'd like
to go even smaller.
- Josh Triplett
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