netdev - Re: [PATCH][RFC 23/23]: Support for zero-copy TCP transmit of user space data

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Message-ID: <20081224180841.GA615@ioremap.net>
Date:	Wed, 24 Dec 2008 21:08:41 +0300
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	Vladislav Bolkhovitin <vst@...b.net>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-scsi@...r.kernel.org,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Mike Christie <michaelc@...wisc.edu>,
	Jeff Garzik <jeff@...zik.org>,
	Boaz Harrosh <bharrosh@...asas.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, scst-devel@...ts.sourceforge.net,
	Bart Van Assche <bart.vanassche@...il.com>,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	netdev@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>,
	David Miller <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>
Subject: Re: [PATCH][RFC 23/23]: Support for zero-copy TCP transmit of user space data

On Wed, Dec 24, 2008 at 08:46:56PM +0300, Vladislav Bolkhovitin (vst@...b.net) wrote:
> I think in most cases there would be possibility to embed 
> sk_transaction_token to some higher level structure. E.g. Xen apparently 
> should have something to track packets passed through host/guest 
> boundary. From other side, kmem cache is too well polished to have much 
> overhead. I doubt, you would even notice it in this application. In most 
> cases allocation of such small object in it using SLUB is just about the 
> same as a list_del() under disabled IRQs.

I definitely would not rely on that, especially at cache reclaim time.
But it of course depends on the workload and maybe appropriate for the
cases in question. The best solution I think is to combine tag and
separate destructur, so that those who do not want to allocate a token
could still get notification via destructor callback.

-- 
	Evgeniy Polyakov
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