From: Sagi Grimberg <sagi@grimberg.me>
To: Hannes Reinecke <hare@suse.de>, linux-nvme@lists.infradead.org
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
Keith Busch <kbusch@kernel.org>,
Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
linux-block@vger.kernel.org
Subject: Re: [PATCH v2 2/2] nvme: support io stats on the mpath device
Date: Tue, 4 Oct 2022 11:19:07 +0300 [thread overview]
Message-ID: <0733f642-8b97-b6ce-8a0e-14c3bb8e2a9a@grimberg.me> (raw)
In-Reply-To: <9db5d7eb-bd84-85e6-c30a-da057f1b2b69@suse.de>
On 10/4/22 09:11, Hannes Reinecke wrote:
> On 10/3/22 11:43, Sagi Grimberg wrote:
>> Our mpath stack device is just a shim that selects a bottom namespace
>> and submits the bio to it without any fancy splitting. This also means
>> that we don't clone the bio or have any context to the bio beyond
>> submission. However it really sucks that we don't see the mpath device
>> io stats.
>>
>> Given that the mpath device can't do that without adding some context
>> to it, we let the bottom device do it on its behalf (somewhat similar
>> to the approach taken in nvme_trace_bio_complete).
>>
>> When the IO starts, we account the request for multipath IO stats using
>> REQ_NVME_MPATH_IO_STATS nvme_request flag to avoid queue io stats disable
>> in the middle of the request.
>>
>> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
>> ---
>> drivers/nvme/host/core.c | 4 ++++
>> drivers/nvme/host/multipath.c | 25 +++++++++++++++++++++++++
>> drivers/nvme/host/nvme.h | 12 ++++++++++++
>> 3 files changed, 41 insertions(+)
>>
>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index 64fd772de817..d5a54ddf73f2 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -384,6 +384,8 @@ static inline void nvme_end_req(struct request *req)
>> nvme_log_error(req);
>> nvme_end_req_zoned(req);
>> nvme_trace_bio_complete(req);
>> + if (req->cmd_flags & REQ_NVME_MPATH)
>> + nvme_mpath_end_request(req);
>> blk_mq_end_request(req, status);
>> }
>> @@ -421,6 +423,8 @@ EXPORT_SYMBOL_GPL(nvme_complete_rq);
>> void nvme_start_request(struct request *rq)
>> {
>> + if (rq->cmd_flags & REQ_NVME_MPATH)
>> + nvme_mpath_start_request(rq);
>> blk_mq_start_request(rq);
>> }
>> EXPORT_SYMBOL_GPL(nvme_start_request);
>
> Why don't you move the check for REQ_NVME_MPATH into
> nvme_mpath_{start,end}_request?
I'm less fond of calling a function that may or may not
do anything...
But it is a pattern that exists in the code, if people prefer
it I can change it.
next prev parent reply other threads:[~2022-10-04 8:19 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-03 9:43 [PATCH v2 0/2] nvme-mpath: Add IO stats support Sagi Grimberg
2022-10-03 9:43 ` [PATCH v2 1/2] nvme: introduce nvme_start_request Sagi Grimberg
2022-10-04 6:09 ` Hannes Reinecke
2022-11-29 14:28 ` Keith Busch
2022-11-29 14:32 ` Jens Axboe
2022-11-29 14:31 ` Jens Axboe
2022-10-03 9:43 ` [PATCH v2 2/2] nvme: support io stats on the mpath device Sagi Grimberg
2022-10-04 6:11 ` Hannes Reinecke
2022-10-04 8:19 ` Sagi Grimberg [this message]
2022-11-29 14:33 ` Jens Axboe
2022-11-29 14:33 ` Jens Axboe
2022-11-29 14:42 ` Keith Busch
2022-11-29 14:45 ` [PATCH v2 0/2] nvme-mpath: Add IO stats support Christoph Hellwig
2022-11-29 16:43 ` Keith Busch
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