[PATCH] nvme/pci: Remove last_cq_head

[PATCH] nvme/pci: Remove last_cq_head

[Keith Busch]

We had been saving the last_cq_head seen from an interrupt so that a
polled queue wouldn't mistakenly trigger spruious interrupt detection. We
don't poll interrupt driven queues any more, so saving this value is
pointless.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 drivers/nvme/host/pci.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 9d307593b94f..0590640ba62c 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -176,7 +176,6 @@ struct nvme_queue {
 	u16 sq_tail;
 	u16 last_sq_tail;
 	u16 cq_head;
-	u16 last_cq_head;
 	u16 qid;
 	u8 cq_phase;
 	u8 sqes;
@@ -1026,10 +1025,7 @@ static irqreturn_t nvme_irq(int irq, void *data)
 	 * the irq handler, even if that was on another CPU.
 	 */
 	rmb();
-	if (nvmeq->cq_head != nvmeq->last_cq_head)
-		ret = IRQ_HANDLED;
 	nvme_process_cq(nvmeq, &start, &end, -1);
-	nvmeq->last_cq_head = nvmeq->cq_head;
 	wmb();
 
 	if (start != end) {
-- 
2.21.0


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Re: [PATCH] nvme/pci: Remove last_cq_head

[Christoph Hellwig]

On Tue, Dec 03, 2019 at 07:18:29AM +0900, Keith Busch wrote:
> We had been saving the last_cq_head seen from an interrupt so that a
> polled queue wouldn't mistakenly trigger spruious interrupt detection. We
> don't poll interrupt driven queues any more, so saving this value is
> pointless.

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Btw, didn't you also have some other patches to shrink the size of
struct nvme_queue from a few months ago?

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Re: [PATCH] nvme/pci: Remove last_cq_head

[Keith Busch]

On Tue, Dec 03, 2019 at 08:36:55AM +0100, Christoph Hellwig wrote:
> On Tue, Dec 03, 2019 at 07:18:29AM +0900, Keith Busch wrote:
> > We had been saving the last_cq_head seen from an interrupt so that a
> > polled queue wouldn't mistakenly trigger spruious interrupt detection. We
> > don't poll interrupt driven queues any more, so saving this value is
> > pointless.
> 
> Looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks, applied for-5.5.
 
> Btw, didn't you also have some other patches to shrink the size of
> struct nvme_queue from a few months ago?

Yes, I need to rebase those and do more testing. As long as no kernel
debugging is enabled, I believe we can fit all the nvmeq hot data in
one 64B cache line.

This was just the first patch. I doubt I'll be able to get the rest
completed for the current merge window, though.

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