linux-kernel - Re: [PATCH] mm: add a new emergency page migratetype.

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Message-ID: <fc866097-f529-158e-8f24-5d42b11d28b1@redhat.com>
Date:   Tue, 7 Jun 2022 14:55:05 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Huanpeng Xin <xinhuanpeng9@...il.com>, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        xinhuanpeng <xinhuanpeng@...omi.com>
Subject: Re: [PATCH] mm: add a new emergency page migratetype.

On 06.06.22 05:27, Huanpeng Xin wrote:
> From: xinhuanpeng <xinhuanpeng@...omi.com>
> 
> add a new page migratetype reserved for
> non-costly non-NOWARN page allocation failure.

Sorry to say, but this patch description is not expressive enough. I
have absolutely no clue what you are trying to achieve and why we should
care.

Especially, why do we care about locally grouping these allocations
(that's what pageblock flags are for after all)?

Your Kconfig option is also not particularly user friendly to read either:

"This enables the migration type MIGRATE_EMERGENCY,which reserves
 a small amount of memory for non-costly non-NOWARN page allocation
 failure."

Usually we reserve memory via different mechanisms, like atomic
reserves? Why can't something like that be used.

On first sight, defining a new pageblock migratype feels wrong to me.
But then, I have no clue what you are actually trying to achieve.

-- 
Thanks,

David / dhildenb