Re: [RFC-v3 9/9] iser-target: Add iSCSI Extensions for RDMA (iSER) target driver

Nicholas A. Bellinger
2013-04-04T22:17:43Z

On Thu, 2013-04-04 at 12:45 +0300, Or Gerlitz wrote:
> On 04/04/2013 10:24, Nicholas A. Bellinger wrote:
>
> > +#define ISER_RECV_DATA_SEG_LEN 8192
> > +#define ISER_RX_PAYLOAD_SIZE (ISER_HEADERS_LEN + ISER_RECV_DATA_SEG_LEN)
> > [...]
> > +#define ISER_RX_PAD_SIZE (16384 - (ISER_RX_PAYLOAD_SIZE + \
> > + sizeof(u64) + sizeof(struct ib_sge)))
>
> We're eating here too much ram for the pad, you need 8K + something, so
> the pad can count down
> from 12K and not 16K which means each such element will consume three
> pages and not four.
>

Hmm, IIRC this larger pad was originally required after bumping the
ISER_RECV_DATA_SEG_LEN value for handling incoming ImmediateData and
Unsolicited Data-OUT.. Will try using 12k here and see what happens..

Also, ISER_RECV_DATA_SEG_LEN will need to be enforced as the largest
MaxRecvDataSegmentLength negotiated during iser login to prevent the
initiator from exceeding the hardcoded value..

> > +struct iser_rx_desc {
> > + struct iser_hdr iser_header;
> > + struct iscsi_hdr iscsi_header;
> > + char data[ISER_RECV_DATA_SEG_LEN];
> > + u64 dma_addr;
> > + struct ib_sge rx_sg;
> > + char pad[ISER_RX_PAD_SIZE];
> > +} __packed;
> > +
> > +struct isert_rx_desc {
> > + struct isert_conn *desc_conn;
> > + struct work_struct desc_work;
> > + struct iser_rx_desc desc;
> > +} __packed;
>
> You have way enough room in the pad field of struct iser_rx_desc to
> place there the two fields
> added by struct isert_rx_desc (and you only use struct iser_rx_desc from
> within isert_rx_desc) --> any reason
> not to unify them?
>

This is left-over cruft from the per isert_rx_desc dispatch into process
context.. Dropping this now.

--nab