From: Ira Weiny <ira.weiny@intel.com>
To: Bernard Metzler <BMT@zurich.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>,
Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>,
Doug Ledford <dledford@redhat.com>,
Faisal Latif <faisal.latif@intel.com>,
Shiraz Saleem <shiraz.saleem@intel.com>,
Kamal Heib <kheib@redhat.com>,
linux-rdma <linux-rdma@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V3] RDMA/siw: Convert siw_tx_hdt() to kmap_local_page()
Date: Thu, 24 Jun 2021 10:33:16 -0700 [thread overview]
Message-ID: <20210624173316.GA2799309@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <OF739F2480.B35209F8-ON002586FE.00569A1A-002586FE.00569A24@ch.ibm.com>
On Thu, Jun 24, 2021 at 03:45:55PM +0000, Bernard Metzler wrote:
>
> >@@ -593,7 +601,7 @@ static int siw_tx_hdt(struct siw_iwarp_tx *c_tx,
> >struct socket *s)
> > } else {
> > rv = kernel_sendmsg(s, &msg, iov, seg + 1,
> > hdr_len + data_len + trl_len);
> >- siw_unmap_pages(page_array, kmap_mask);
> >+ siw_unmap_pages(iov, kmap_mask, seg+1);
>
> seg+1 is one to many, since the last segment references the iWarp
> trailer (CRC). There are 2 reason for this multi-segment processing
> in the transmit path. (1) efficiency and (2) MTU based packet framing.
> The iov contains the complete iWarp frame with header, (potentially
> multiple) data fragments, and the CRC. It gets pushed to TCP in one
> go, praying for iWarp framing stays intact (which most time works).
> So the code can collect data form multiple SGE's of a WRITE or
> SEND and tries putting those into one frame, if MTU allows, and
> adds header and trailer.
>
> The last segment (seg + 1) references the CRC, which is never kmap'ed.
siw_unmap_pages() take a length and seg is the index...
But ok so a further optimization...
Fair enough.
>
> I'll try the code next days, but it looks good otherwise!
I believe this will work though.
Ira
> Thanks very much!
> > }
> > if (rv < (int)hdr_len) {
> > /* Not even complete hdr pushed or negative rv */
> >--
> >2.28.0.rc0.12.gb6a658bd00c9
> >
> >
next prev parent reply other threads:[~2021-06-24 17:33 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 6:14 [PATCH 0/4] Remove use of kmap() ira.weiny
2021-06-22 6:14 ` [PATCH 1/4] RDMA/hfi1: " ira.weiny
2021-06-24 18:13 ` Jason Gunthorpe
2021-06-22 6:14 ` [PATCH 2/4] RDMA/i40iw: " ira.weiny
2021-06-22 12:14 ` Jason Gunthorpe
2021-06-22 16:56 ` [PATCH V2] RDMA/irdma: " ira.weiny
2021-06-24 18:13 ` Jason Gunthorpe
2021-06-22 6:14 ` [PATCH 3/4] RDMA/siw: Remove kmap() ira.weiny
2021-07-15 18:00 ` Jason Gunthorpe
2021-06-22 6:14 ` [PATCH 4/4] RDMA/siw: Convert siw_tx_hdt() to kmap_local_page() ira.weiny
2021-06-22 20:34 ` [PATCH V2] " ira.weiny
2021-06-23 22:15 ` [PATCH V3] " ira.weiny
2021-06-24 17:48 ` [PATCH V4] " ira.weiny
2021-07-15 18:00 ` Jason Gunthorpe
2021-06-29 14:11 ` Bernard Metzler
2021-06-29 22:13 ` Ira Weiny
2021-06-24 15:45 ` [PATCH V3] " Bernard Metzler
2021-06-24 17:33 ` Ira Weiny [this message]
2021-06-23 14:36 ` [PATCH V2] " Bernard Metzler
2021-06-23 15:34 ` Ira Weiny
2021-06-22 16:42 ` [PATCH 4/4] " Bernard Metzler
2021-06-22 20:39 ` Ira Weiny
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