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lf-6.6.y
linux-imx/Documentation/ABI/testing/sysfs-kernel-mm-swap
Huang Ying 61b639723b mm, swap: use page-cluster as max window of VMA based swap readahead 
When the VMA based swap readahead was introduced, a new knob

  /sys/kernel/mm/swap/vma_ra_max_order

was added as the max window of VMA swap readahead.  This is to make it
possible to use different max window for VMA based readahead and
original physical readahead.  But Minchan Kim pointed out that this will
cause a regression because setting page-cluster sysctl to zero cannot
disable swap readahead with the change.

To fix the regression, the page-cluster sysctl is used as the max window
of both the VMA based swap readahead and original physical swap
readahead.  If more fine grained control is needed in the future, more
knobs can be added as the subordinate knobs of the page-cluster sysctl.

The vma_ra_max_order knob is deleted.  Because the knob was introduced
in v4.14-rc1, and this patch is targeting being merged before v4.14
releasing, there should be no existing users of this newly added ABI.

Link: http://lkml.kernel.org/r/20171011070847.16003-1-ying.huang@intel.com
Fixes: ec560175c0 ("mm, swap: VMA based swap readahead")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-10-13 16:18:33 -07:00

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What: /sys/kernel/mm/swap/ Date: August 2017 Contact: Linux memory management mailing list linux-mm@kvack.org Description: Interface for swapping

What: /sys/kernel/mm/swap/vma_ra_enabled Date: August 2017 Contact: Linux memory management mailing list linux-mm@kvack.org Description: Enable/disable VMA based swap readahead.

	If set to true, the VMA based swap readahead algorithm
	will be used for swappable anonymous pages mapped in a
	VMA, and the global swap readahead algorithm will be
	still used for tmpfs etc. other users.  If set to
	false, the global swap readahead algorithm will be
	used for all swappable pages.