netdev - Re: [PATCH net-next 1/2] vhost_net: mitigate page reference counting during page frag refill

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Message-Id: <20181117.120105.1022512033566284108.davem@davemloft.net>
Date:   Sat, 17 Nov 2018 12:01:05 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     jasowang@...hat.com
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] vhost_net: mitigate page reference
 counting during page frag refill

From: Jason Wang <jasowang@...hat.com>
Date: Thu, 15 Nov 2018 17:43:09 +0800

> We do a get_page() which involves a atomic operation. This patch tries
> to mitigate a per packet atomic operation by maintaining a reference
> bias which is initially USHRT_MAX. Each time a page is got, instead of
> calling get_page() we decrease the bias and when we find it's time to
> use a new page we will decrease the bias at one time through
> __page_cache_drain_cache().
> 
> Testpmd(virtio_user + vhost_net) + XDP_DROP on TAP shows about 1.6%
> improvement.
> 
> Before: 4.63Mpps
> After:  4.71Mpps
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Applied.