linux-kernel - Re: Raise initial congestion window size / speedup slow start?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4C3E0684.5060409@wildgooses.com>
Date:	Wed, 14 Jul 2010 19:48:36 +0100
From:	Ed W <lists@...dgooses.com>
To:	David Miller <davem@...emloft.net>
CC:	davidsen@....com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: Raise initial congestion window size / speedup slow start?

On 14/07/2010 19:15, David Miller wrote:
> From: Bill Davidsen<davidsen@....com>
> Date: Wed, 14 Jul 2010 11:21:15 -0400
>
>    
>> You may have to go into /proc/sys/net/core and crank up the
>> rmem_* settings, depending on your distribution.
>>      
> You should never, ever, have to touch the various networking sysctl
> values to get good performance in any normal setup.  If you do, it's a
> bug, report it so we can fix it.
>    

Just checking the basics here because I don't think this is a bug so 
much as a, less common installation that differs from the "normal" case.

- When we create a tcp connection we always start with tcp slow start
- This sets the congestion window to effectively 4 packets?
- This applies in both directions?
- Remote sender responds to my hypothetical http request with the first 
4 packets of data
- We need to wait one RTT for the ack to come back and now we can send 
the next 8 packets,
- Wait for the next ack and at 16 packets we are now moving at a 
sensible fraction of the bandwidth delay product?

So just to be clear:
- We don't seem to have any user-space tuning knobs to influence this 
right now?
- In this age of short attention spans, a couple of extra seconds 
between clicking something and it responding is worth optimising (IMHO)
- I think I need to take this to netdev, but anyone else with any ideas 
happy to hear them?

Thanks

Ed W
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/