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mm: zswap: remove same_filled module params

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These knobs offer more fine-grained control to userspace than needed and
directly expose/influence kernel implementation; remove them.

For disabling same_filled handling, there is no logical reason to refuse
storing same-filled pages more efficiently and opt for compression. 
Scanning pages for patterns may be an argument, but the page contents will
be read into the CPU cache anyway during compression.  Also, removing the
same_filled handling code does not move the needle significantly in terms
of performance anyway [1].

For disabling non_same_filled handling, it was added when the compressed
pages in zswap were not being properly charged to memcgs, as workloads
could escape the accounting with compression [2].  This is no longer the
case after commit f4840ccfca ("zswap: memcg accounting"), and using
zswap without compression does not make much sense.

[1]https://lore.kernel.org/lkml/CAJD7tkaySFP2hBQw4pnZHJJwe3bMdjJ1t9VC2VJd=khn1_TXvA@mail.gmail.com/
[2]https://lore.kernel.org/lkml/19d5cdee-2868-41bd-83d5-6da75d72e940@maciej.szmigiero.name/

[yosryahmed@google.com: remove same_filled_pages from docs]
  Link: https://lkml.kernel.org/r/ZhxFVggdyvCo79jc@google.com
Link: https://lkml.kernel.org/r/20240413022407.785696-5-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yosry Ahmed
2024-04-13 02:24:07 +00:00
committed by Andrew Morton
parent e87b881489
commit c074e1467f
3 changed files with 0 additions and 50 deletions
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2
Documentation/driver-api/crypto/iaa/iaa-crypto.rst
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@@ -457,7 +457,6 @@ Use the following commands to enable zswap::
# echo deflate-iaa > /sys/module/zswap/parameters/compressor
# echo zsmalloc > /sys/module/zswap/parameters/zpool
# echo 1 > /sys/module/zswap/parameters/enabled
# echo 0 > /sys/module/zswap/parameters/same_filled_pages_enabled
# echo 100 > /proc/sys/vm/swappiness
# echo never > /sys/kernel/mm/transparent_hugepage/enabled
# echo 1 > /proc/sys/vm/overcommit_memory
@@ -599,7 +598,6 @@ the 'fixed' compression mode::
echo deflate-iaa > /sys/module/zswap/parameters/compressor
echo zsmalloc > /sys/module/zswap/parameters/zpool
echo 1 > /sys/module/zswap/parameters/enabled
echo 0 > /sys/module/zswap/parameters/same_filled_pages_enabled
echo 100 > /proc/sys/vm/swappiness
echo never > /sys/kernel/mm/transparent_hugepage/enabled