linux-kernel - Re: [PATCH v1 1/2] zsmalloc: add allocated objects counter for subpage

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Message-ID: <20230620103629.GA42985@google.com>
Date:   Tue, 20 Jun 2023 19:36:29 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Alexey Romanov <avromanov@...rdevices.ru>
Cc:     minchan@...nel.org, senozhatsky@...omium.org,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel@...rdevices.ru
Subject: Re: [PATCH v1 1/2] zsmalloc: add allocated objects counter for
 subpage

On (23/06/19 17:35), Alexey Romanov wrote:
> 
> We use a variable of type unsigned int to store the offset
> of the first object at the subpage In turn, the offset cannot
> exceed the size of PAGE_SIZE, which is usually 4096. Thus,
> 12 bits are enough to store the offset.

[..]

> If the page size is 4Kb

It's certainly not a given. PAGE_SIZE is architecture specific.
PAGE_SIZE_16KB and PAGE_SIZE_64KB would be simple examples, but there
are, apparently, architectures that even can have PAGE_SIZE_256KB.