linux-kernel - Re: [PATCH v2] mm/zsmalloc: don't need to reserve LSB in handle

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Date: Wed, 28 Feb 2024 12:26:33 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Chengming Zhou <chengming.zhou@...ux.dev>
Cc: minchan@...nel.org, senozhatsky@...omium.org, akpm@...ux-foundation.org,
	hannes@...xchg.org, nphamcs@...il.com, yosryahmed@...gle.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/zsmalloc: don't need to reserve LSB in handle

On (24/02/28 02:38), Chengming Zhou wrote:
> We will save allocated tag in the object header to indicate that it's
> allocated.
> 
> 	handle |= OBJ_ALLOCATED_TAG;
> 
> So the object header needs to reserve LSB for this tag bit.
> 
> But the handle itself doesn't need to reserve LSB to save tag, since
> it's only used to find the position of object, by (pfn + obj_idx).
> So remove LSB reserve from handle, one more bit can be used as obj_idx.
> 
> Signed-off-by: Chengming Zhou <chengming.zhou@...ux.dev>

Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>