linux-toradex.git/include/linux/frontswap.h, branch v6.4-rc1

frontswap: remove support for multiple ops

2022-01-22T06:33:38+00:00

There is only a single instance of frontswap ops in the kernel, so
simplify the frontswap code by removing support for multiple operations.

Link: https://lkml.kernel.org/r/20211224062246.1258487-13-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove frontswap_test

2022-01-22T06:33:38+00:00

frontswap_test is unused now, remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-10-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: simplify try_to_unuse

2022-01-22T06:33:38+00:00

Remove the unused frontswap and pages_to_unuse arguments, and mark the
function static now that the caller in frontswap is gone.

[akpm@linux-foundation.org: fix shmem_unuse() stub, per Matthew]

Link: https://lkml.kernel.org/r/20211224062246.1258487-9-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Cc: Naresh Kamboju 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: simplify frontswap_init

2022-01-22T06:33:38+00:00

Just use IS_ENABLED() and remove the __frontswap_init indirection.

Also remove the unused export.

Link: https://lkml.kernel.org/r/20211224062246.1258487-7-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove frontswap_curr_pages

2022-01-22T06:33:38+00:00

frontswap_curr_pages is never called, so remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-6-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove frontswap_shrink

2022-01-22T06:33:38+00:00

frontswap_shrink is never called, so remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-5-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove frontswap_tmem_exclusive_gets

2022-01-22T06:33:38+00:00

frontswap_tmem_exclusive_gets is never called, so remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-4-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

frontswap: remove frontswap_writethrough

2022-01-22T06:33:38+00:00

frontswap_writethrough is never called, so remove it.

Link: https://lkml.kernel.org/r/20211224062246.1258487-3-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Juergen Gross 
Cc: Dan Streetman 
Cc: Geert Uytterhoeven 
Cc: Hugh Dickins 
Cc: Konrad Rzeszutek Wilk 
Cc: Matthew Wilcox (Oracle) 
Cc: Seth Jennings 
Cc: Vitaly Wool 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

include/linux/frontswap.h: drop duplicated word in a comment

2020-08-12T17:57:57+00:00

Drop the doubled word "in" in a comment.

Signed-off-by: Randy Dunlap 
Signed-off-by: Andrew Morton 
Reviewed-by: Andrew Morton 
Cc: Konrad Rzeszutek Wilk 
Link: http://lkml.kernel.org/r/3af7ed91-ad62-8445-40a4-9e07a64b9523@infradead.org
Signed-off-by: Linus Torvalds

mm: rid swapoff of quadratic complexity

2019-03-06T05:07:18+00:00

This patch was initially posted by Kelley Nielsen.  Reposting the patch
with all review comments addressed and with minor modifications and
optimizations.  Also, folding in the fixes offered by Hugh Dickins and
Huang Ying.  Tests were rerun and commit message updated with new
results.

try_to_unuse() is of quadratic complexity, with a lot of wasted effort.
It unuses swap entries one by one, potentially iterating over all the
page tables for all the processes in the system for each one.

This new proposed implementation of try_to_unuse simplifies its
complexity to linear.  It iterates over the system's mms once, unusing
all the affected entries as it walks each set of page tables.  It also
makes similar changes to shmem_unuse.

Improvement

swapoff was called on a swap partition containing about 6G of data, in a
VM(8cpu, 16G RAM), and calls to unuse_pte_range() were counted.

Present implementation....about 1200M calls(8min, avg 80% cpu util).
Prototype.................about  9.0K calls(3min, avg 5% cpu util).

Details

In shmem_unuse(), iterate over the shmem_swaplist and, for each
shmem_inode_info that contains a swap entry, pass it to
shmem_unuse_inode(), along with the swap type.  In shmem_unuse_inode(),
iterate over its associated xarray, and store the index and value of
each swap entry in an array for passing to shmem_swapin_page() outside
of the RCU critical section.

In try_to_unuse(), instead of iterating over the entries in the type and
unusing them one by one, perhaps walking all the page tables for all the
processes for each one, iterate over the mmlist, making one pass.  Pass
each mm to unuse_mm() to begin its page table walk, and during the walk,
unuse all the ptes that have backing store in the swap type received by
try_to_unuse().  After the walk, check the type for orphaned swap
entries with find_next_to_unuse(), and remove them from the swap cache.
If find_next_to_unuse() starts over at the beginning of the type, repeat
the check of the shmem_swaplist and the walk a maximum of three times.

Change unuse_mm() and the intervening walk functions down to
unuse_pte_range() to take the type as a parameter, and to iterate over
their entire range, calling the next function down on every iteration.
In unuse_pte_range(), make a swap entry from each pte in the range using
the passed in type.  If it has backing store in the type, call
swapin_readahead() to retrieve the page and pass it to unuse_pte().

Pass the count of pages_to_unuse down the page table walks in
try_to_unuse(), and return from the walk when the desired number of
pages has been swapped back in.

Link: http://lkml.kernel.org/r/20190114153129.4852-2-vpillai@digitalocean.com
Signed-off-by: Vineeth Remanan Pillai 
Signed-off-by: Kelley Nielsen 
Signed-off-by: Huang Ying 
Acked-by: Hugh Dickins 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds