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From: Varun Prakash <varun@chelsio.com>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: target-devel@vger.kernel.org, linux-scsi@vger.kernel.org,
	nab@linux-iscsi.org, swise@opengridcomputing.com,
	kxie@chelsio.com, indranil@chelsio.com
Subject: Re: [PATCH v2 01/16] iscsi-target: add callback to alloc and free PDU
Date: Wed, 13 Apr 2016 21:51:30 +0530	[thread overview]
Message-ID: <20160413162129.GA1680@chelsio.com> (raw)
In-Reply-To: <570E17C9.3010204@grimberg.me>

On Wed, Apr 13, 2016 at 12:56:25PM +0300, Sagi Grimberg wrote:
> 
> >>On 09/04/16 16:11, Varun Prakash wrote:
> >>>Add two callbacks to struct iscsit_transport -
> >>>
> >>>1. void *(*iscsit_alloc_pdu)()
> >>>    iscsi-target uses this callback for
> >>>    iSCSI PDU allocation.
> >>>
> >>>2. void (*iscsit_free_pdu)
> >>>    iscsi-target uses this callback
> >>>    to free an iSCSI PDU which was
> >>>    allocated by iscsit_alloc_pdu().
> >>
> >>Can you please explain why are you adding two different
> >>callouts? Who (Chelsio T5) will need it, and why they can't
> >>use the in-cmd pdu?
> >
> >I am adding these to avoid per PDU 48 bytes(BHS) memcpy from cmd->pdu to
> >transport driver tx buffer, iscsi-target can directly form iscsi hdr
> >in transport driver tx buffer.
> 
> Is that what it's for? Looks meaningless to me, do
> you have an indication that this is some sort of bottleneck?
> 
> I see you memset in your pdu_alloc, where is the gain
> here anyway?

We can definitely avoid memcpy if iscsi-target fills all
the fields in iscsi hdr, in current code some fields
are assumed to be zero so a memset is required in transport
driver.
I will drop this patch in -v3, thanks. 

  reply	other threads:[~2016-04-13 16:21 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-09 13:11 [PATCH v2 00/16] Chelsio iSCSI target offload driver Varun Prakash
2016-04-09 13:11 ` [PATCH v2 01/16] iscsi-target: add callback to alloc and free PDU Varun Prakash
2016-04-10 17:33   ` Sagi Grimberg
2016-04-11 14:54     ` Varun Prakash
2016-04-13  9:56       ` Sagi Grimberg
2016-04-13 16:21         ` Varun Prakash [this message]
2016-04-09 13:11 ` [PATCH v2 02/16] iscsi-target: add int (*iscsit_xmit_pdu)() Varun Prakash
2016-04-10 17:36   ` Sagi Grimberg
2016-04-09 13:11 ` [PATCH v2 03/16] iscsi-target: add int (*iscsit_xmit_datain_pdu)() Varun Prakash
2016-04-10 17:38   ` Sagi Grimberg
2016-04-11 16:12     ` Varun Prakash
2016-04-09 13:11 ` [PATCH v2 04/16] iscsi-target: add void (*iscsit_release_cmd)() Varun Prakash
2016-04-10 17:42   ` Sagi Grimberg
2016-04-11 17:16     ` Varun Prakash
2016-04-09 13:11 ` [PATCH v2 05/16] iscsi-target: add void (*iscsit_get_rx_pdu)() Varun Prakash
2016-04-10 17:43   ` Sagi Grimberg
2016-04-09 13:11 ` [PATCH v2 06/16] iscsi-target: split iscsi_target_rx_thread() Varun Prakash
2016-04-09 13:11 ` [PATCH v2 07/16] iscsi-target: add int (*iscsit_validate_params)() Varun Prakash
2016-04-10 17:50   ` Sagi Grimberg
2016-04-11 17:44     ` Varun Prakash
2016-04-09 13:11 ` [PATCH v2 08/16] iscsi-target: add void (*iscsit_get_r2t_ttt)() Varun Prakash
2016-04-10 17:51   ` Sagi Grimberg
2016-04-11 18:08     ` Varun Prakash
2016-04-13  9:52       ` Sagi Grimberg
2016-04-13 13:03         ` Varun Prakash
2016-04-09 13:11 ` [PATCH v2 09/16] iscsi-target: move iscsit_thread_check_cpumask() Varun Prakash
2016-04-09 13:11 ` [PATCH v2 10/16] iscsi-target: use conn->network_transport in text rsp Varun Prakash
2016-04-10 17:55   ` Sagi Grimberg
2016-04-09 13:11 ` [PATCH v2 11/16] iscsi-target: add new offload transport type Varun Prakash
2016-04-10 17:56   ` Sagi Grimberg
2016-04-09 13:11 ` [PATCH v2 12/16] iscsi-target: clear tx_thread_active Varun Prakash
2016-04-09 13:11 ` [PATCH v2 13/16] iscsi-target: call complete on conn_logout_comp Varun Prakash
2016-04-09 13:11 ` [PATCH v2 14/16] iscsi-target: export symbols Varun Prakash
2016-04-09 13:11 ` [PATCH v2 15/16] iscsi-target: fix seq_end_offset calculation Varun Prakash
2016-04-10 17:59   ` Sagi Grimberg
2016-04-09 13:11 ` [PATCH v2 16/16] cxgbit: add files for cxgbit.ko Varun Prakash

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