linux-kernel - Re: [PATCH] mm, swap: Make VMA based swap readahead configurable

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Message-ID: <20170926132129.dbtr2mof35x4j4og@dhcp22.suse.cz>
Date:   Tue, 26 Sep 2017 15:21:29 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
        Rik van Riel <riel@...hat.com>, Shaohua Li <shli@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Tim Chen <tim.c.chen@...el.com>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH] mm, swap: Make VMA based swap readahead configurable

On Thu 21-09-17 09:33:10, Huang, Ying wrote:
> From: Huang Ying <ying.huang@...el.com>
> 
> This patch adds a new Kconfig option VMA_SWAP_READAHEAD and wraps VMA
> based swap readahead code inside #ifdef CONFIG_VMA_SWAP_READAHEAD/#endif.
> This is more friendly for tiny kernels.

How (much)?

> And as pointed to by Minchan
> Kim, give people who want to disable the swap readahead an opportunity
> to notice the changes to the swap readahead algorithm and the
> corresponding knobs.

Why would anyone want that?

Please note that adding new config options make the already complicated
config space even more problematic so there should be a good reason to
add one. Please make sure your justification is clear on why this is
worth the future maintenance and configurability burden.
-- 
Michal Hocko
SUSE Labs