linux-kernel - Re: [PATCH 10/19] x86, mpx: trace ranged MPX operations

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Date:	Mon, 18 May 2015 23:04:18 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dave Hansen <dave@...1.net>
cc:	linux-kernel@...r.kernel.org, x86@...nel.org,
	dave.hansen@...ux.intel.com
Subject: Re: [PATCH 10/19] x86, mpx: trace ranged MPX operations

On Fri, 8 May 2015, Dave Hansen wrote:
> When MPX can not free an entire bounds table, it will instead
> try to zap unused parts of a bounds table to free the backing
> memory.  This decreases RSS (resident set size) without
> decreasing the virtual space allocated for bounds tables.
> 
> trace attempts to find bounds tables:

My first reading was: "The trace attempts to find bounds tables"

"Trace the attempts to find bounds tables" is what you actually mean.

> This event traces any time we go looking to unmap a bounds table

You have two events ....

> for a given virtual address range.  This is useful to ensure
> that the kernel actually "tried" to free a bounds table versus
> times it succeeded.
> 
> It might try and fail if it realized that a table was shared
> with an adjacent VMA which is not being unmapped.

So rewording that would probably create a useful changelog.

Thanks,

	tglx
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