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Subject: Re: [PATCH 1/4] net/skbuff: don't waste memory reserves
To:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        "David S. Miller" <davem@davemloft.net>
Cc:     Eric Dumazet <edumazet@google.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Willem de Bruijn <willemb@google.com>,
        Florian Westphal <fw@strlen.de>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org
References: <20190418180524.23489-1-aryabinin@virtuozzo.com>
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From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <a80606cf-3076-b01d-0442-ccff3c462276@gmail.com>
Date:   Fri, 19 Apr 2019 06:41:37 -0700
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On 04/19/2019 06:17 AM, Andrey Ryabinin wrote:
> 

> I don't see why that would be a problem. If refill failed because we didn't have
> access to reserves, then there going to be an another refill attempt, right?
> And the next refill attempt will be with access to the reserves if memalloc socket was created.
> We can't predict the future, so until the memalloc socket appeared we must assume that those
> RX ring buffers won't be used to reclaim memory (and that is actually true in 99% of cases).
> 

I just said that the alloc might be attempted "in the past"

Yes, we can not predict the future, this is why we need to access the reserve _now_ and not
at the time the packet is received.

The 'being true in 99% of cases' argument is not really convincing.

You want the NIC to be ready to receive packets even before sk_memalloc_socks() becomes true.

If a NIC driver has a bug, please fix it.