netdev - Re: BUG: sk_backlog.len can overestimate

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Date:   Tue, 1 Oct 2019 16:01:41 -0700
From:   John Ousterhout <ouster@...stanford.edu>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: BUG: sk_backlog.len can overestimate

On Tue, Oct 1, 2019 at 1:53 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> On 10/1/19 1:45 PM, John Ousterhout wrote:
>
> >
> > But this isn't really about socket resource limits (though that is
> > conflated in the implementation); it's about limiting the time spent
> > in a single call to __release_sock, no?
>
> The proxy used is memory usage, not time usage.

I apologize for being pedantic, but the proxy isn't memory usage; it's
actually "number of bytes added to the backlog since the last time it
was emptied". At the time the limit is hit, actual memory usage is
probably a lot less than the limit. This was the source of my
confusion, since I assumed you really *wanted* memory usage to be the
limit.

> cond_resched() or a preemptible kernel makes anything based on time flaky,
> you probably do not want to play with a time limit...
>
>
>