netdev - Re: [RFC] GRO scalability

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: <1349500126.4883.4.camel@edumazet-laptop>
Date:	Sat, 06 Oct 2012 07:08:46 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>, Jesse Gross <jesse@...ira.com>
Subject: Re: [RFC] GRO scalability

Le samedi 06 octobre 2012 à 12:11 +0800, Herbert Xu a écrit :
> On Fri, Oct 05, 2012 at 04:52:27PM +0200, Eric Dumazet wrote:
> > Current GRO cell is somewhat limited :
> > 
> > - It uses a single list (napi->gro_list) of pending skbs
> > 
> > - This list has a limit of 8 skbs (MAX_GRO_SKBS)
> > 
> > - Workloads with lot of concurrent flows have small GRO hit rate but
> >   pay high overhead (in inet_gro_receive())
> > 
> > - Increasing MAX_GRO_SKBS is not an option, because GRO
> >   overhead becomes too high.
> 
> Yeah these were all meant to be addressed at some point.
> 
> > - Packets can stay a long time held in GRO cell (there is
> >   no flush if napi never completes on a stressed cpu)
> 
> This should never happen though.  NAPI runs must always be
> punctuated just to guarantee one card never hogs a CPU.  Which
> driver causes these behaviour?

I believe its a generic issue, not specific to a driver.

napi_gro_flush() is only called from napi_complete() 

Some drivers (marvell/skge.c & realtek/8139cp.c) calls it only because
they 'inline' napi_complete()



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html