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

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Date: Thu, 13 Jun 2024 20:58:55 +0800
From: Jisheng Zhang <jszhang@...nel.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Minchan Kim <minchan@...nel.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 Thu, Jun 13, 2024 at 12:17:31PM +0900, Sergey Senozhatsky wrote:
> 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)?

I think yes copy_page performs better than memcpy(PAGE_SIZE)
commit afb2d666d025 ("zsmalloc: use copy_page for full page copy")
also shows the result.