linux-kernel - Re: [PATCH v2 15/23] percpu: introduce bitmap metadata blocks

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Message-ID: <20170725192057.GO18880@destiny>
Date:   Tue, 25 Jul 2017 15:20:57 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     Dennis Zhou <dennisz@...com>
Cc:     Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Josef Bacik <josef@...icpanda.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-team@...com, Dennis Zhou <dennisszhou@...il.com>
Subject: Re: [PATCH v2 15/23] percpu: introduce bitmap metadata blocks

On Mon, Jul 24, 2017 at 07:02:12PM -0400, Dennis Zhou wrote:
> From: "Dennis Zhou (Facebook)" <dennisszhou@...il.com>
> 
> This patch introduces the bitmap metadata blocks and adds the skeleton
> of the code that will be used to maintain these blocks.  Each chunk's
> bitmap is made up of full metadata blocks. These blocks maintain basic
> metadata to help prevent scanning unnecssarily to update hints. Full
> scanning methods are used for the skeleton and will be replaced in the
> coming patches. A number of helper functions are added as well to do
> conversion of pages to blocks and manage offsets. Comments will be
> updated as the final version of each function is added.
> 
> There exists a relationship between PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE,
> the region size, and unit_size. Every chunk's region (including offsets)
> is page aligned at the beginning to preserve alignment. The end is
> aligned to LCM(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE) to ensure that the end
> can fit with the populated page map which is by page and every metadata
> block is fully accounted for. The unit_size is already page aligned, but
> must also be aligned with PCPU_BITMAP_BLOCK_SIZE to ensure full metadata
> blocks.
> 
> Signed-off-by: Dennis Zhou <dennisszhou@...il.com>

Reviewed-by: Josef Bacik <jbacik@...com>

Thanks,

Josef