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Date: Tue, 27 Feb 2024 16:52:09 +0900
From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: chengming.zhou@linux.dev
Cc: minchan@kernel.org, senozhatsky@chromium.org, akpm@linux-foundation.org,
	hannes@cmpxchg.org, nphamcs@gmail.com, yosryahmed@google.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Chengming Zhou <zhouchengming@bytedance.com>
Subject: Re: [PATCH] mm/zsmalloc: don't need to save tag bit in handle
Message-ID: <20240227075209.GA11972@google.com>
References: <20240227030045.3443702-1-chengming.zhou@linux.dev>
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On (24/02/27 03:00), chengming.zhou@linux.dev wrote:
> 
> We only need to save the position (pfn + obj_idx) in the handle, don't
> need to save tag bit in handle. So one more bit can be used as obj_idx.

[..]

> mm/zsmalloc: don't need to save tag bit in handle

Does this mean "don't need to reserve LSB for tag"?
We still save allocated tag in the handle, that's what

	handle |= OBJ_ALLOCATED_TAG;

does.

> Actually, the tag bit is only useful in zspage's memory space, to tell
> if an object is allocated or not.

I'm not completely sure if I follow this sentence.