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From: Johannes Weiner <hannes@cmpxchg.org>
To: Dave Gordon <david.s.gordon@intel.com>
Cc: linux-mm@kvack.org, intel-gfx@lists.freedesktop.org,
	Michal Hocko <mhocko@kernel.org>,
	"Goel, Akash" <akash.goel@intel.com>
Subject: Re: [PATCH v3] mm: Export {__}get_nr_swap_pages()
Date: Thu, 17 Dec 2015 14:45:45 -0500	[thread overview]
Message-ID: <20151217194545.GA27852@cmpxchg.org> (raw)
In-Reply-To: <1450376144-32792-1-git-send-email-david.s.gordon@intel.com>

On Thu, Dec 17, 2015 at 06:15:44PM +0000, Dave Gordon wrote:
> Some modules, like i915.ko, use swappable objects and may try to swap
> them out under memory pressure (via the shrinker). Before doing so,
> they want to check using get_nr_swap_pages() to see if any swap space
> is available as otherwise they will waste time purging the object from
> the device without recovering any memory for the system. This requires
> the kernel function get_nr_swap_pages() to be exported to the modules.
> 
> The current implementation of this function is as a static inline
> inside the header file swap.h>; this doesn't work when compiled in
> a module, as the necessary global data is not visible. The original
> proposed solution was to export the kernel global variable to modules,
> but this was considered poor practice as it exposed more than necessary,
> and in an uncontrolled fashion. Another idea was to turn it into a real
> (non-inline) function; however this was considered to unnecessarily add
> overhead for users within the base kernel.
> 
> Therefore, to avoid both objections, this patch leaves the base kernel
> implementation unchanged, but adds a separate (read-only) functional
> interface for callers in loadable kernel modules (LKMs). Which definition
> is visible to code depends on the compile-time symbol MODULE, defined
> by the Kbuild system when building an LKM.

I'm sorry, but this is beyond silly. 19 lines of code to fix a
non-existent problem? This lacks any sort of proportionality.

NAK
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx

WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes@cmpxchg.org>
To: Dave Gordon <david.s.gordon@intel.com>
Cc: intel-gfx@lists.freedesktop.org,
	Chris Wilson <chris@chris-wilson.co.uk>,
	"Goel, Akash" <akash.goel@intel.com>,
	Michal Hocko <mhocko@kernel.org>,
	linux-mm@kvack.org
Subject: Re: [PATCH v3] mm: Export {__}get_nr_swap_pages()
Date: Thu, 17 Dec 2015 14:45:45 -0500	[thread overview]
Message-ID: <20151217194545.GA27852@cmpxchg.org> (raw)
In-Reply-To: <1450376144-32792-1-git-send-email-david.s.gordon@intel.com>

On Thu, Dec 17, 2015 at 06:15:44PM +0000, Dave Gordon wrote:
> Some modules, like i915.ko, use swappable objects and may try to swap
> them out under memory pressure (via the shrinker). Before doing so,
> they want to check using get_nr_swap_pages() to see if any swap space
> is available as otherwise they will waste time purging the object from
> the device without recovering any memory for the system. This requires
> the kernel function get_nr_swap_pages() to be exported to the modules.
> 
> The current implementation of this function is as a static inline
> inside the header file swap.h>; this doesn't work when compiled in
> a module, as the necessary global data is not visible. The original
> proposed solution was to export the kernel global variable to modules,
> but this was considered poor practice as it exposed more than necessary,
> and in an uncontrolled fashion. Another idea was to turn it into a real
> (non-inline) function; however this was considered to unnecessarily add
> overhead for users within the base kernel.
> 
> Therefore, to avoid both objections, this patch leaves the base kernel
> implementation unchanged, but adds a separate (read-only) functional
> interface for callers in loadable kernel modules (LKMs). Which definition
> is visible to code depends on the compile-time symbol MODULE, defined
> by the Kbuild system when building an LKM.

I'm sorry, but this is beyond silly. 19 lines of code to fix a
non-existent problem? This lacks any sort of proportionality.

NAK

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  reply	other threads:[~2015-12-17 19:46 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-04 15:58 [PATCH v2 1/2] mm: Export nr_swap_pages Chris Wilson
2015-12-04 15:58 ` [PATCH v2 2/2] drm/i915: Disable shrinker for non-swapped backed objects Chris Wilson
2015-12-04 15:58   ` Chris Wilson
2015-12-04 16:11   ` Johannes Weiner
2015-12-04 16:11     ` Johannes Weiner
2015-12-10  9:34   ` Daniel Vetter
2015-12-04 16:09 ` [PATCH v2 1/2] mm: Export nr_swap_pages Johannes Weiner
2015-12-04 16:09   ` Johannes Weiner
2015-12-10  9:32   ` [Intel-gfx] " Daniel Vetter
2015-12-23 22:04     ` Johannes Weiner
2015-12-23 22:04       ` [Intel-gfx] " Johannes Weiner
2015-12-23 22:26       ` Andrew Morton
2016-01-05 10:05         ` Daniel Vetter
2015-12-07 13:48 ` Michal Hocko
2015-12-07 16:48   ` Johannes Weiner
2015-12-07 16:48     ` Johannes Weiner
2015-12-07 17:04     ` Michal Hocko
2015-12-07 18:02       ` Johannes Weiner
2015-12-07 18:02         ` Johannes Weiner
2015-12-07 18:10     ` [Intel-gfx] " Dave Gordon
2015-12-07 19:13       ` Johannes Weiner
2015-12-08 11:19         ` Dave Gordon
2015-12-08 11:19           ` [Intel-gfx] " Dave Gordon
2015-12-08 11:22         ` Michal Hocko
2015-12-08 11:22           ` [Intel-gfx] " Michal Hocko
2015-12-17 18:15           ` [PATCH v3] mm: Export {__}get_nr_swap_pages() Dave Gordon
2015-12-17 18:15             ` Dave Gordon
2015-12-17 19:45             ` Johannes Weiner [this message]
2015-12-17 19:45               ` Johannes Weiner

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