Date:   Wed, 24 Nov 2021 16:37:07 -0500
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Suren Baghdasaryan <surenb@google.com>
Cc:     akpm@linux-foundation.org, mhocko@suse.com, mcgrof@kernel.org,
        keescook@chromium.org, yzaikin@google.com,
        dave.hansen@linux.intel.com, vbabka@suse.cz,
        mgorman@techsingularity.net, corbet@lwn.net, yi.zhang@huawei.com,
        xi.fengfei@h3c.com, rppt@kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        kernel-team@android.com
Subject: Re: [PATCH 1/1] sysctl: change watermark_scale_factor max limit to
 30%
Message-ID: <YZ6wg9A5p5WUy7+k@cmpxchg.org>
References: <20211124193604.2758863-1-surenb@google.com>
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On Wed, Nov 24, 2021 at 11:36:04AM -0800, Suren Baghdasaryan wrote:
> For embedded systems with low total memory, having to run applications
> with relatively large memory requirements, 10% max limitation for
> watermark_scale_factor poses an issue of triggering direct reclaim
> every time such application is started. This results in slow application
> startup times and bad end-user experience.
> By increasing watermark_scale_factor max limit we allow vendors more
> flexibility to choose the right level of kswapd aggressiveness for
> their device and workload requirements.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

No objection from me as this limit was always totally arbitrary. But I
have to say I'm a bit surprised: The current maximum setting will wake
kswapd when free memory drops below 10% and have it reclaim until
20%. This seems like quite a lot? Are there applications that really
want kswapd to wake at 30% and target 60% of memory free?