linux-kernel - Re: [PATCH] add blockconsole version 1.1

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Date:	Tue, 24 Jul 2012 22:28:20 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Jörn Engel <joern@...fs.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Jeff Moyer <jmoyer@...hat.com>,
	Steve Hodgson <steve@...estorage.com>
Subject: Re: [PATCH] add blockconsole version 1.1

On Tue, Jul 24, 2012 at 01:52:32PM -0400, Jörn Engel wrote:
> On Tue, 24 July 2012 18:25:47 +0200, Borislav Petkov wrote:
> > > The advantage should be better robustness, in particular when dealing
> > > with cheap flash devices.
> > 
> > In the sense that we flush the current sector after one second the
> > latest so that we can lose as small amount of data as possible if the
> > system crashes right at that point?
> 
> In the sense that cheap devices don't always handle rewrites of the
> same sector well.  Often this results in the entire erase block being
> rewritten, causing bad performance and wear-out.  Many cheap devices
> aren't real block devices.  They are barely good enough to support
> FAT and may die near-instantly with a different write pattern.
> Blockconsole assumes utter crap as an underlying device.
> 
> The timer mainly ensures that, on a quiet system, those two lines of
> output from half an hour ago actually make it to the device
> eventually.  In the case of a crash, the panic notifier is supposed to
> do the same for those messages you _really_ care about.
> 
> > Ok, I see what you mean. I see a red line in vim here. Ok, good to know,
> > maybe this feature with the empty lines could be in the docs too so
> > people don't ask that question again?
> 
> Last paragraph. ;)
> 
> > Or you issue a tag instead of an empty line like so:
> > 
> > [   10.498422] console [bcon0] enabled
> > [   10.499899] blockconsole: now logging to /dev/sdc at 1
> > [   10.594791] usb 5-2: new full-speed USB device number 3 using ohci_hcd
> > <<LOG timeout of 1sec>>
> > [   12.665911] xhci_hcd 0000:00:10.0: xHCI Host Controller
> > [   12.668469] xhci_hcd 0000:00:10.0: new USB bus registered, assigned bus number 6
> > 
> > which explains everything.
> 
> That would only work if you have at least 26 bytes to pad.  Bunch of
> spaces with a newline works for any value between 0 and 512.

Ok, thanks for taking the time to explain this - very interesting stuff.

So, as far as I'm concerned blockconsole is ready for shipping! 8-)

-- 
Regards/Gruss,
    Boris.
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