linux-kernel - Re: [PATCH v3 7/7] zram: writeback throttle

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Message-ID: <20181203023040.GA427@jagdpanzerIV>
Date:   Mon, 3 Dec 2018 11:30:40 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joey Pabalinas <joeypabalinas@...il.com>
Subject: Re: [PATCH v3 7/7] zram: writeback throttle

On (12/03/18 08:18), Minchan Kim wrote:
> 
> Per andrew's comment:
> https://lkml.org/lkml/2018/11/27/156
> 
> I need to fix it to represent 4K always.

Aha.

Then we need to increase bd_writes PAGE_SIZE/4K times in writeback_store()?

   wb_count = atomic64_inc_return(&zram->stats.bd_writes);
   ...
   if (wb_limit != 0 && wb_count >= wb_limit)
       zram->stop_writeback = true;

bd_wb_limit is in 4K units; but in writeback_store() we alloc a full page
and write it to the backing device. So the actual number of written bytes
can be larger on systems with page_size > 4K. Right?

	-ss