linux-kernel - Re: [PATCH v2 12/23] percpu: increase minimum percpu allocation size and align first regions

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Message-ID: <20170725183351.GL18880@destiny>
Date:   Tue, 25 Jul 2017 14:33:52 -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 12/23] percpu: increase minimum percpu allocation size
 and align first regions

On Mon, Jul 24, 2017 at 07:02:09PM -0400, Dennis Zhou wrote:
> From: "Dennis Zhou (Facebook)" <dennisszhou@...il.com>
> 
> This patch increases the minimum allocation size of percpu memory to
> 4-bytes. This change will help minimize the metadata overhead
> associated with the bitmap allocator. The assumption is that most
> allocations will be of objects or structs greater than 2 bytes with
> integers or longs being used rather than shorts.
> 
> The first chunk regions are now aligned with the minimum allocation
> size. The reserved region is expected to be set as a multiple of the
> minimum allocation size. The static region is aligned up and the delta
> is removed from the dynamic size. This works because the dynamic size is
> increased to be page aligned. If the static size is not minimum
> allocation size aligned, then there must be a gap that is added to the
> dynamic size. The dynamic size will never be smaller than the set value.
> 
> Signed-off-by: Dennis Zhou <dennisszhou@...il.com>

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

Thanks,

Josef