[dpdk-dev] [PATCH] cycles: add isb before read cntvct_el0

[Jerin Jacob]

On Tue, Mar 10, 2020 at 8:09 AM Linhaifeng <haifeng.lin at huawei.com> wrote:
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> -----邮件原件-----
> 发件人: Jerin Jacob [mailto:jerinjacobk at gmail.com]
> 发送时间: 2020年3月9日 23:43
> 收件人: Linhaifeng <haifeng.lin at huawei.com>
> 抄送: dev at dpdk.org; thomas at monjalon.net; Lilijun (Jerry) <jerry.lilijun at huawei.com>; chenchanghu <chenchanghu at huawei.com>; xudingke <xudingke at huawei.com>
> 主题: Re: [dpdk-dev] [PATCH] cycles: add isb before read cntvct_el0
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> On Mon, Mar 9, 2020 at 2:43 PM Linhaifeng <haifeng.lin at huawei.com> wrote:
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> > We nead isb rather than dsb to sync system counter to cntvct_el0.
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> # Currently rte_rdtsc() does not have dsb. Right? or any barriers.
> # Why do you need it? If it regarding, getting accurate value then use rte_rdtsc_precise().
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> We use rte_get_tsc_cycles get start_value in pmd1 and end_value in pmd2 in our qos module, it works ok in x86 but not ok in arm64.
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> Then we use rte_mb() to sync instruction but it not work.Because rte_mb is dsb I think it only have affect on memory. cntvct_el0 and system counter is register so I think we should use isb.
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> It works well after we use isb in multi core scenes.
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> Use rte_rdtsc_precise is good idea. Maybe use isb replace of rte_mb(dsb) ?

Yes. Please.


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> > Signed-off-by: Haifeng Lin <haifeng.lin at huawei.com>