linux-kernel - Re: [PATCH V2 1/2] percpu_ref: reduce memory footprint of percpu

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Date:   Wed, 2 Sep 2020 15:44:35 +0200
From:   Christoph Hellwig <hch@....de>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        Sagi Grimberg <sagi@...mberg.me>, Tejun Heo <tj@...nel.org>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Bart Van Assche <bvanassche@....org>
Subject: Re: [PATCH V2 1/2] percpu_ref: reduce memory footprint of
 percpu_ref in fast path

On Wed, Sep 02, 2020 at 08:26:42PM +0800, Ming Lei wrote:
> 'struct percpu_ref' is often embedded into one user structure, and the
> instance is usually referenced in fast path, however actually only
> 'percpu_count_ptr' is needed in fast path.
> 
> So move other fields into one new structure of 'percpu_ref_data', and
> allocate it dynamically via kzalloc(), then memory footprint of
> 'percpu_ref' in fast path is reduced a lot and becomes suitable to put
> into hot cacheline of user structure.

This looks good:

Reviewed-by: Christoph Hellwig <hch@....de>