netdev - Re: [PATCH iproute2 net-next v2 3/4] ss: Buffer raw fields first, then render them as a table

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Message-ID: <20190213085101.7474ba5d@shemminger-XPS-13-9360>
Date:   Wed, 13 Feb 2019 08:51:01 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Stefano Brivio <sbrivio@...hat.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
        Sabrina Dubroca <sd@...asysnail.net>
Subject: Re: [PATCH iproute2 net-next v2 3/4] ss: Buffer raw fields first,
 then render them as a table

On Wed, 13 Feb 2019 09:37:11 +0100
Stefano Brivio <sbrivio@...hat.com> wrote:

> On Tue, 12 Feb 2019 16:42:04 -0800
> Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> > I do not get it.
> > 
> > "ss -emoi " uses almost 1KB per socket.
> > 
> > 10,000,000 sockets -> we need about 10GB of memory  ???
> > 
> > This is a serious regression.  
> 
> I guess this is rather subjective: the worst case I considered back then
> was the output of 'ss -tei0' (less than 500 bytes) for one million
> sockets, which gives 500M of memory, which should in turn be fine on a
> machine handling one million sockets.
> 
> Now, if 'ss -emoi' on 10 million sockets is an actual use case (out of
> curiosity: how are you going to process that output? Would JSON help?),
> I see two easy options to solve this:
> 
> 1. flush the output every time we reach a given buffer size (1M
>    perhaps). This might make the resulting blocks slightly unaligned,
>    with occasional loss of readability on lines occurring every 1k to
>    10k sockets approximately, even though after 1k sockets column sizes
>    won't change much (it looks anyway better than the original), and I
>    don't expect anybody to actually scroll that output
> 
> 2. add a switch for unbuffered output, but then you need to remember to
>    pass it manually, and the whole output would be as bad as the
>    original in case you need the switch.
> 
> I'd rather go with 1., it's easy to implement (we already have partial
> flushing with '--events') and it looks like a good compromise on
> usability. Thoughts?
> 

I agree with eric. The benefits of buffering are not worth it.
Let's just choose a reasonable field width, if something is too big, columns won't line up
which i snot a big deal.

Unless you come up with a better solution, I am going to revert this.