Commit 64dd89ae authored by Johannes Weiner's avatar Johannes Weiner Committed by Andrew Morton
Browse files

mm/block/fs: remove laptop_mode 

Laptop mode was introduced to save battery, by delaying and consolidating
writes and thereby maximize the time rotating hard drives wouldn't have to
spin.

Luckily, rotating hard drives, with their high spin-up times and power
draw, are a thing of the past for battery-powered devices.  Reclaim has
also since changed to not write single filesystem pages anymore, and
regular filesystem writeback is lumpy by design.

The juice doesn't appear worth the squeeze anymore.  The footprint of the
feature is small, but nevertheless it's a complicating factor in mm,
block, filesystems.  Developers don't think about it, and it likely hasn't
been tested with new reclaim and writeback changes in years.

Let's sunset it.  Keep the sysctl with a deprecation warning around for a
few more cycles, but remove all functionality behind it.

[akpm@linux-foundation.org: fix Documentation/admin-guide/laptops/index.rst]
Link: https://lkml.kernel.org/r/20251216185201.GH905277@cmpxchg.org


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Suggested-by: default avatarChristoph Hellwig <hch@infradead.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarJens Axboe <axboe@kernel.dk>
Reviewed-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Deepanshu Kartikey <kartikey406@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 657a81fe

Documentation/admin-guide/laptops/index.rst

+0 −1
Original line number Diff line number Diff line
@@ -10,7 +10,6 @@ Laptop Drivers 
   alienware-wmi

   asus-laptop

   disk-shock-protection

   laptop-mode

   lg-laptop

   samsung-galaxybook

   sony-laptop

Documentation/admin-guide/laptops/laptop-mode.rst

deleted100644 → 0
+0 −770

File deleted.

Preview size limit exceeded, changes collapsed.

Documentation/admin-guide/sysctl/vm.rst

+0 −8
Original line number Diff line number Diff line
@@ -41,7 +41,6 @@ Currently, these files are in /proc/sys/vm: 
- extfrag_threshold

- highmem_is_dirtyable

- hugetlb_shm_group

- laptop_mode

- legacy_va_layout

- lowmem_reserve_ratio

- max_map_count
@@ -363,13 +362,6 @@ hugetlb_shm_group contains group id that is allowed to create SysV 
shared memory segment using hugetlb page.





laptop_mode

===========



laptop_mode is a knob that controls "laptop mode". All the things that are

controlled by this knob are discussed in Documentation/admin-guide/laptops/laptop-mode.rst.





legacy_va_layout

================

block/blk-mq.c

+0 −3
Original line number Diff line number Diff line
@@ -811,9 +811,6 @@ void blk_mq_free_request(struct request *rq) 


	blk_mq_finish_request(rq);



	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))

		laptop_io_completion(q->disk->bdi);



	rq_qos_done(q, rq);



	WRITE_ONCE(rq->state, MQ_RQ_IDLE);

fs/ext4/inode.c

+1 −2
Original line number Diff line number Diff line
@@ -3305,8 +3305,7 @@ int ext4_alloc_da_blocks(struct inode *inode) 
	/*

	 * We do something simple for now.  The filemap_flush() will

	 * also start triggering a write of the data blocks, which is

	 * not strictly speaking necessary (and for users of

	 * laptop_mode, not even desirable).  However, to do otherwise

	 * not strictly speaking necessary.  However, to do otherwise

	 * would require replicating code paths in:

	 *

	 * ext4_writepages() ->