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From: Bart Van Assche <Bart.VanAssche@sandisk.com>
To: "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"target-devel@vger.kernel.org" <target-devel@vger.kernel.org>,
	"sagi@grimberg.me" <sagi@grimberg.me>
Subject: Re: [PATCH rfc 06/10] IB/cq: Don't force IB_POLL_DIRECT poll context for ib_process_cq_direct
Date: Tue, 14 Mar 2017 21:32:12 +0000	[thread overview]
Message-ID: <1489527119.2676.15.camel@sandisk.com> (raw)
In-Reply-To: <f4ade02b-9d17-20ae-f910-47c718f2a5bd@grimberg.me>

On Mon, 2017-03-13 at 10:24 +0200, Sagi Grimberg wrote:
> > Before this patch
> > the completions from each CQ were processed sequentially. That's a big
> > change so I think this should be mentioned clearly in the header above
> > ib_process_cq_direct().
>=20
> Note that I now see that the cq lock is not sufficient for mutual
> exclusion here because we're referencing cq->wc array outside of it.
>=20
> There are three options I see here:
> 1. we'll need to allocate a different wc array for polling mode,
> perhaps a smaller one?
> 2. Export __ib_process_cq (in some form) with an option to pass in a wc
> array.
> 3. Simply not support non-selective polling but it seems like a shame...
>=20
> Any thoughts?

I doubt it is possible to come up with an algorithm that recognizes whether
or not two different ib_process_cq() calls are serialized. So the
ib_process_cq() caller will have to provide that information. How about add=
ing
an ib_wc array argument to ib_process_cq() and modifying __ib_process_cq()
such that it uses that array if specified and cq->wc otherwise?

Bart.=

  reply	other threads:[~2017-03-14 21:34 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-09 13:16 [PATCH rfc 00/10] non selective polling block interface Sagi Grimberg
2017-03-09 13:16 ` [PATCH rfc 01/10] nvme-pci: Split __nvme_process_cq to poll and handle Sagi Grimberg
2017-03-09 13:57   ` Johannes Thumshirn
2017-03-22 19:07   ` Christoph Hellwig
2017-03-09 13:16 ` [PATCH rfc 02/10] nvme-pci: Add budget to __nvme_process_cq Sagi Grimberg
2017-03-09 13:46   ` Johannes Thumshirn
2017-03-22 19:08   ` Christoph Hellwig
2017-03-09 13:16 ` [PATCH rfc 03/10] nvme-pci: open-code polling logic in nvme_poll Sagi Grimberg
2017-03-09 13:56   ` Johannes Thumshirn
2017-03-22 19:09   ` Christoph Hellwig
2017-03-09 13:16 ` [PATCH rfc 04/10] block: Add a non-selective polling interface Sagi Grimberg
2017-03-09 13:44   ` Johannes Thumshirn
2017-03-10  3:04     ` Damien Le Moal
2017-03-13  8:26       ` Sagi Grimberg
2017-03-09 16:25   ` Bart Van Assche
2017-03-13  8:15     ` Sagi Grimberg
2017-03-14 21:21       ` Bart Van Assche
2017-03-09 13:16 ` [PATCH rfc 05/10] nvme-pci: Support blk_poll_batch Sagi Grimberg
2017-03-09 13:16 ` [PATCH rfc 06/10] IB/cq: Don't force IB_POLL_DIRECT poll context for ib_process_cq_direct Sagi Grimberg
2017-03-09 16:30   ` Bart Van Assche
2017-03-13  8:24     ` Sagi Grimberg
2017-03-14 21:32       ` Bart Van Assche [this message]
2017-03-09 13:16 ` [PATCH rfc 07/10] nvme-rdma: Don't rearm the CQ when polling directly Sagi Grimberg
2017-03-09 13:52   ` Johannes Thumshirn
2017-03-09 13:16 ` [PATCH rfc 08/10] nvme-rdma: Support blk_poll_batch Sagi Grimberg
2017-03-09 13:16 ` [PATCH rfc 09/10] nvmet: Use non-selective polling Sagi Grimberg
2017-03-09 13:54   ` Johannes Thumshirn
2017-03-09 13:16 ` [PATCH rfc 10/10] target: " Sagi Grimberg
2017-03-18 23:58   ` Nicholas A. Bellinger
2017-03-21 11:35     ` Sagi Grimberg

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