From: "liuqi (BA)" <liuqi115@huawei.com>
To: Will Deacon <will@kernel.org>, Linuxarm <linuxarm@huawei.com>
Cc: <mark.rutland@arm.com>, <bhelgaas@google.com>,
<linux-pci@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <zhangshaokun@hisilicon.com>
Subject: Re: [PATCH v8 2/2] drivers/perf: hisi: Add driver for HiSilicon PCIe PMU
Date: Wed, 4 Aug 2021 15:29:54 +0800 [thread overview]
Message-ID: <a56266c4-c434-f078-6027-f30c021bd593@huawei.com> (raw)
In-Reply-To: <20210802100343.GA27282@willie-the-truck>
Hi Will,
> Hmm, I was hoping that you would expose all the events as proper perf_events
> and get rid of the subevents entirely.
>
> Then userspace could do things like:
>
> // Count number of RX memory reads
> $ perf stat -e hisi_pcie0_0/rx_memory_read/
>
> // Count delay cycles
> $ perf stat -e hisi_pcie0_0/latency/
>
> // Count both of the above (events must be in the same group)
> $ perf stat -g -e hisi_pcie0_0/latency/ -e hisi_pcie0_0/rx_memory_read/
>
> Note that in all three of these cases the hardware will be programmed in
> the same way and both HISI_PCIE_CNT and HISI_PCIE_EXT_CNT are allocated!
>
> So for example, doing this (i.e. without the '-g'):
>
> $ perf stat -e hisi_pcie0_0/latency/ -e hisi_pcie0_0/rx_memory_read/
>
> would fail because the first event would allocate both of the counters.
I'm confused with this situation when getting rid of subevent:
$ perf stat -e hisi_pcie0_0/latency/ -e hisi_pcie0_0/rx_memory_read/
In this case, driver checks the relationship of "latency" and
"rx_memory_read" in pmu->add() function and return a -EINVAL, but this
seems lead to time division multiplexing.
if (event->pmu->add(event, PERF_EF_START)) {
perf_event_set_state(event, PERF_EVENT_STATE_INACTIVE);
event->oncpu = -1;
ret = -EAGAIN;
goto out;
}
...
out:
perf_pmu_enable(event->pmu);
This result doesn't meet our expection, do I miss something here?
How about add an array to record events and check the relationship in
event_init() function? It seems that perf stat could only failed when
driver return invalid value in pmu->event_init() function.
Thanks,
Qi
>
> All you need to do is check the counter scheduling constraints when
> accepting an event group in the driver. No need for subevents at all.
>
> Does that make sense?
>
> Will
> .
>
next prev parent reply other threads:[~2021-08-04 7:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-28 8:09 [PATCH v8 0/2] drivers/perf: hisi: Add support for PCIe PMU Qi Liu
2021-07-28 8:09 ` [PATCH v8 1/2] docs: perf: Add description for HiSilicon PCIe PMU driver Qi Liu
2021-07-28 8:09 ` [PATCH v8 2/2] drivers/perf: hisi: Add driver for HiSilicon PCIe PMU Qi Liu
2021-08-02 10:03 ` Will Deacon
2021-08-04 7:29 ` liuqi (BA) [this message]
2021-08-13 14:40 ` Will Deacon
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