From: Vladislav Bolkhovitin <vst@vlnb•net>
To: Evgeniy Polyakov <zbr@ioremap•net>
Cc: Herbert Xu <herbert@gondor•apana.org.au>,
Jeremy Fitzhardinge <jeremy@goop•org>,
linux-scsi@vger•kernel.org,
James Bottomley <James.Bottomley@HansenPartnership•com>,
Andrew Morton <akpm@linux-foundation•org>,
FUJITA Tomonori <fujita.tomonori@lab•ntt.co.jp>,
Mike Christie <michaelc@cs•wisc.edu>,
Jeff Garzik <jeff@garzik•org>,
Boaz Harrosh <bharrosh@panasas•com>,
Linus Torvalds <torvalds@linux-foundation•org>,
linux-kernel@vger•kernel.org, scst-devel@lists•sourceforge.net,
Bart Van Assche <bart.vanassche@gmail•com>,
"Nicholas A. Bellinger" <nab@linux-iscsi•org>,
netdev@vger•kernel.org, Rusty Russell <rusty@rustcorp•com.au>,
David Miller <davem@davemloft•net>,
Alexey Kuznetsov <kuznet@ms2•inr.ac.ru>
Subject: Re: [PATCH][RFC 23/23]: Support for zero-copy TCP transmit of user space data
Date: Tue, 23 Dec 2008 22:16:25 +0300 [thread overview]
Message-ID: <49513909.1050100@vlnb.net> (raw)
In-Reply-To: <20081220103209.GA23632@ioremap.net>
Evgeniy Polyakov, on 12/20/2008 01:32 PM wrote:
> On Sat, Dec 20, 2008 at 07:10:45PM +1100, Herbert Xu (herbert@gondor•apana.org.au) wrote:
>>> Hm. So if I get a destructor call from the shared_info, can I go an
>>> inspect the page refcounts to see if its really the last use?
>> The pages that were originally in the shared_info at creation
>> time may no longer be there by the time it's freed because of
>> pskb_pull_tail.
>
> Things should work fine, since pskb_expand_head() copies whole shared
> info structure (and thus will copy destructor), get all pages and then
> copy all pointers into the new skb, and then release old skb's data.
>
> So destructor for the pages should not rely on which skb it is called on
> and check if pages are about to be really freed (i.e. check theirs
> reference counter).
>
> __pskb_pull_tail() is tricky, it just puts some pages it does not want
> to be present in the skb, but it could be possible to add there
> destructor callback from the original skb with partial flag (or just
> having destructor with two parameters: skb and page, and if page is not
> NULL, then actually only given page is freed, otherwise the whole skb).
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.. :-(
Vlad
next prev parent reply other threads:[~2008-12-23 19:16 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-10 18:26 [PATCH][RFC 0/23] New SCSI target framework (SCST) and 4 target drivers Vladislav Bolkhovitin
2008-12-10 19:01 ` [PATCH][RFC 21/23]: iSCSI target driver Vladislav Bolkhovitin
2008-12-11 22:55 ` Nicholas A. Bellinger
2008-12-11 22:59 ` Nicholas A. Bellinger
2008-12-12 19:26 ` Vladislav Bolkhovitin
2008-12-10 19:02 ` [PATCH][RFC 22/23]: Documentation for iSCSI-SCST Vladislav Bolkhovitin
2008-12-10 19:04 ` [PATCH][RFC 23/23]: Support for zero-copy TCP transmit of user space data Vladislav Bolkhovitin
2008-12-10 21:45 ` Evgeniy Polyakov
2008-12-11 18:16 ` Vladislav Bolkhovitin
2008-12-11 19:12 ` James Bottomley
2008-12-12 19:25 ` Vladislav Bolkhovitin
2008-12-12 19:37 ` James Bottomley
2008-12-15 17:58 ` Vladislav Bolkhovitin
2008-12-15 23:18 ` Christoph Hellwig
2008-12-16 18:57 ` Vladislav Bolkhovitin
2008-12-18 18:35 ` [RFC]: " Vladislav Bolkhovitin
2008-12-18 18:43 ` David M. Lloyd
2008-12-19 17:37 ` Vladislav Bolkhovitin
2008-12-19 19:07 ` Jens Axboe
2008-12-19 19:17 ` Vladislav Bolkhovitin
2008-12-19 19:27 ` Jens Axboe
2008-12-19 21:58 ` Evgeniy Polyakov
2008-12-23 19:11 ` Vladislav Bolkhovitin
2008-12-19 11:27 ` Andi Kleen
2008-12-19 17:38 ` Vladislav Bolkhovitin
2008-12-19 18:00 ` Andi Kleen
2008-12-19 17:57 ` Vladislav Bolkhovitin
2008-12-16 16:00 ` [PATCH][RFC 23/23]: " Bart Van Assche
2008-12-16 17:41 ` Evgeniy Polyakov
2008-12-19 20:21 ` Jeremy Fitzhardinge
2008-12-19 22:04 ` Evgeniy Polyakov
2008-12-19 22:21 ` Jeremy Fitzhardinge
2008-12-19 22:33 ` Evgeniy Polyakov
2008-12-20 1:56 ` Jeremy Fitzhardinge
2008-12-20 2:02 ` Herbert Xu
2008-12-20 6:14 ` Jeremy Fitzhardinge
2008-12-20 6:51 ` Herbert Xu
2008-12-20 7:43 ` Jeremy Fitzhardinge
2008-12-20 8:10 ` Herbert Xu
2008-12-20 10:32 ` Evgeniy Polyakov
2008-12-20 19:39 ` Jeremy Fitzhardinge
2008-12-22 0:43 ` Rusty Russell
2008-12-23 19:14 ` Vladislav Bolkhovitin
2008-12-23 19:16 ` Vladislav Bolkhovitin [this message]
2008-12-23 21:38 ` Evgeniy Polyakov
2008-12-24 14:37 ` Vladislav Bolkhovitin
2008-12-24 14:44 ` Evgeniy Polyakov
2008-12-24 17:46 ` Vladislav Bolkhovitin
2008-12-24 18:08 ` Evgeniy Polyakov
2008-12-30 17:37 ` Vladislav Bolkhovitin
2008-12-30 21:35 ` Evgeniy Polyakov
2008-12-23 19:13 ` Vladislav Bolkhovitin
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