linux-kernel - Re: [PATCH] zram: use copy

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Date: Thu, 13 Jun 2024 12:17:31 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Jisheng Zhang <jszhang@...nel.org>
Cc: Minchan Kim <minchan@...nel.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org
Subject: Re: [PATCH] zram: use copy_page for full page copy

On (24/06/13 08:04), Jisheng Zhang wrote:
> commit 42e99bd975fd ("zram: optimize memory operations with
> clear_page()/copy_page()") optimize page copy/clean operations, but
> then commit d72e9a7a93e4 ("zram: do not use copy_page with non-page
> aligned address") removes the optimization because there's memory
> corruption at that time, the reason was well explained. But after
> commit 1f7319c74275 ("zram: partial IO refactoring"), partial IO uses
> alloc_page() instead of kmalloc to allocate a page, so we can bring
> back the optimization.
> 
> commit 80ba4caf8ba9 ("zram: use copy_page for full page copy") brings
> back partial optimization, missed one point in zram_write_page().
> optimize the full page copying in zram_write_page() with copy_page()

Is copy_page() really more optimal than memcpy(PAGE_SIZE)?