linux-kernel - Re: [PATCH] xen/blback: Fit the important information of the thread in 17 characters

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Date:	Fri, 19 Feb 2016 16:40:04 +0100
From:	Roger Pau Monné <roger.pau@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH] xen/blback: Fit the important information of the thread
 in 17 characters

El 17/2/16 a les 17:31, Konrad Rzeszutek Wilk ha escrit:
> The processes names are truncated to 17, while we had the length
> of the process as name 20 - which meant that while we filled
> it out with various details - the last 3 characters (which had
> the queue number) never surfaced to the user-space.
> 
> To simplify this and be able to fit the device name, domain id,
> and the queue number we remove the 'blkback' from the name.
> 
> Prior to this patch the device name is "blkback.<domid>.<name>"
> for example: blkback.8.xvda, blkback.11.hda.
> 
> With the multiqueue block backend we add "-%d" for the queue.
> But sadly this is already way past the limit so it gets stripped.
> 
> Possible solution had been identified by Ian:
> http://lists.xenproject.org/archives/html/xen-devel/2015-05/msg03516.html
> 
>   "
>   If you are pressed for space then the "xvd" is probably a bit redundant
>   in a string which starts blkbk.
> 
>   The guest may not even call the device xvdN (iirc BSD has another
>   prefix) any how, so having blkback say so seems of limited use anyway.
> 
>   Since this seems to not include a partition number how does this work in
>   the split partition scheme? (i.e. one where the guest is given xvda1 and
>   xvda2 rather than xvda with a partition table)
> 
> [It will be 'blkback.8.xvda1', and 'blkback.11.xvda2']
> 
>   Perhaps something derived from one of the schemes in
>   http://xenbits.xen.org/docs/unstable/misc/vbd-interface.txt might be a
>   better fit?
> 
> After a bit of discussion (see
> http://lists.xenproject.org/archives/html/xen-devel/2015-12/msg01588.html)
> we settled on dropping the "blback" part.
> 
> This will make it possible to have the <domid>.<name>-<queue>:
> 
>  [1.xvda-0]
>  [1.xvda-1]
> 
> And we enough space to make it go up to:
> 
>  [32100.xvdfg9-5]
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Acked-by: Roger Pau Monné <roger.pau@...rix.com>

According to:

http://lists.xenproject.org/archives/html/xen-devel/2015-05/msg03505.html

Should this have a:

Reported-by: Jan Beulich <jbeulich@...e.com>

Thanks!