Messages in this thread | | | Date | Mon, 12 Oct 2009 14:20:23 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] panic.c: export panic_on_oops |
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* David Woodhouse <dwmw2@infradead.org> wrote:
> On Mon, 2009-10-12 at 14:09 +0200, Ingo Molnar wrote: > > Also, would it be possible to just simplify the thing and not do any > > buffering at all? Extra buffering complexity in a console driver is only > > asking for trouble. Or is flash storage write cycles optimization that > > important in this case? > > That and the fact that on NAND flash you have to write full pages at a > time -- that's 512 bytes, 2KiB or 4KiB depending on the type of chip. > So we really do want to buffer it where we can. > > We don't want to write a 2KiB page for every line of printk output.
Then i think the buffering is at the wrong place: we should instead buffer in the generic layer and pass it to lowlevel if we know that we have gone past a 2K boundary.
The size of the generic log buffer is always a power of two so detecting 2K boundaries is very easy. On any emergency the generic console layer will do faster flushes - this is nothing the console driver itself should bother with.
And that would avoid the whole workqueue logic - which is fragile to be done in a printk to begin with.
So what we need is an extension to struct console that sets a buffering limit. Zero (the default) means unbuffered.
(Btw., things like netconsole might make use of such buffering too.)
Agreed?
Ingo
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