From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: [PATCH][RFC 23/23]: Support for zero-copy TCP transmit of user space data Date: Wed, 24 Dec 2008 17:37:51 +0300 Message-ID: <4952493F.10508@vlnb.net> References: <494C1E5E.7070809@goop.org> <20081219223314.GA2736@ioremap.net> <494C50BB.5030809@goop.org> <20081220020250.GA15064@gondor.apana.org.au> <494C8D57.7040808@goop.org> <20081220065105.GA16936@gondor.apana.org.au> <494CA226.9000200@goop.org> <20081220081045.GA17439@gondor.apana.org.au> <20081220103209.GA23632@ioremap.net> <49513909.1050100@vlnb.net> <20081223213817.GB16883@ioremap.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.126.187]:60132 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751816AbYLXOlf (ORCPT ); Wed, 24 Dec 2008 09:41:35 -0500 In-Reply-To: <20081223213817.GB16883@ioremap.net> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Evgeniy Polyakov Cc: Herbert Xu , Jeremy Fitzhardinge , linux-scsi@vger.kernel.org, James Bottomley , Andrew Morton , FUJITA Tomonori , Mike Christie , Jeff Garzik , Boaz Harrosh , Linus Torvalds , linux-kernel@vger.kernel.org, scst-devel@lists.sourceforge.net, Bart Van Assche , "Nicholas A. Bellinger" , netdev@vger.kernel.org, Rusty Russell , David Miller , Alexey Kuznetsov Evgeniy Polyakov, on 12/24/2008 12:38 AM wrote: > On Tue, Dec 23, 2008 at 10:16:25PM +0300, Vladislav Bolkhovitin (vst@vlnb.net) wrote: >> Actually, there's another way, which seems to be a lot simpler. Alexey >> Kuznetsov privately suggested it to me. >> >> In skb_shared_info new pointer transaction_token would be added, which >> would point on: >> >> struct sk_transaction_token >> { >> atomic_t io_count; >> struct sk_transaction_token *next; >> unsigned long token; >> unsigned long private; >> void (*finish_callback)(struct >> sk_transaction_token *); >> }; >> >> When skb is translated, transaction_token inherited. If 2 skb are merged >> (the same places where I put net_get_page's in my patch), the *older* >> token is inherited. This is the main point of this idea. >> >> Before starting new asynchronous send a client would open a new token. >> Everything sent then would receive that token. Finish_callback() would >> be called and the corresponding token freed, when io_count == 0 *AND* >> all previous tokens closed. >> >> This idea seems to be simpler, than even what Rusty implemented. Correct >> me, if I wrong. But, unfortunately, in the near future I will have no >> time to develop it.. :-( > > Yes, it is simpler and cleaner, but it requires additional allocation. > This is additional (and quite noticeble) overhead. Not necessary requires. For instance, in iscsi-scst sk_transaction_token can (and should) be part of iSCSI cmd structure, so no additional allocations would be needed. Thanks, Vlad