linux-kernel - [PATCH] zswap: change zswap's default allocator to zsmalloc

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Message-Id: <20230908235115.2943486-1-nphamcs@gmail.com>
Date:   Fri,  8 Sep 2023 16:51:15 -0700
From:   Nhat Pham <nphamcs@...il.com>
To:     akpm@...ux-foundation.org
Cc:     hannes@...xchg.org, cerasuolodomenico@...il.com,
        yosryahmed@...gle.com, sjenning@...hat.com, ddstreet@...e.org,
        vitaly.wool@...sulko.com, linux-mm@...ck.org, kernel-team@...a.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH] zswap: change zswap's default allocator to zsmalloc

Out of zswap's 3 allocators, zsmalloc is the clear superior in terms of
memory utilization, both in theory and as observed in practice, with its
high storage density and low internal fragmentation. zsmalloc is also
more actively developed and maintained, since it is the allocator of
choice for zswap for many users, as well as the only allocator for zram.

A historical objection to the selection of zsmalloc as the default
allocator for zswap is its lack of writeback capability. However, this
has changed, with the zsmalloc writeback patchset, and the subsequent
zswap LRU refactor. With this, there is not a lot of good reasons to
keep zbud, an otherwise inferior allocator, as the default instead of
zswap.

This patch changes the default allocator to zsmalloc. The only exception
is on settings without MMU, in which case zbud will remain as the
default.

Signed-off-by: Nhat Pham <nphamcs@...il.com>
---
 mm/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index 721dc88423c7..e0217deca084 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -130,6 +130,7 @@ config ZSWAP_COMPRESSOR_DEFAULT
 choice
 	prompt "Default allocator"
 	depends on ZSWAP
+	default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
 	default ZSWAP_ZPOOL_DEFAULT_ZBUD
 	help
 	  Selects the default allocator for the compressed cache for
-- 
2.34.1