Re:Re: need help for avoiding system calls while using URCU (Userspace RCU)

["方锴 via lttng-dev" <lttng-dev@lists.lttng.org>]

dear Mathieu<br/>  Thank you for your guidance, I've found DKDP's URCU successfully avoids system calls. Grateful for your support!<br/>Best regards,<br/>fangkai
At 2025-03-07 00:58:21, "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com> wrote:
>On 2025-03-06 11:17, Kienan Stewart via lttng-dev wrote:
>> Hi 方锴,
>> 
>> On 3/4/25 3:09 AM, 方锴 via lttng-dev wrote:
>> 
>>> I have referenced your project, URCU (Userspace RCU), on GitHub, which 
>>> is based on the QSBR model. However, I 
>> noticed that when using it in user mode, it makes system calls to enter 
>> the kernel. Could you please provide guidance on how to address this issue?
>> 
>> Are there specific parts of the API that you need to be user-space only?
>> 
>>  > I aim to achieve a pure user-mode implementation. Specifically, I 
>> would appreciate any insights or suggestions on avoiding system calls 
>> while still maintaining the functionality of the QSBR model in user 
>> space. Thank you very much for your time and assistance.
>> 
>> Currently the locking is done using futexs, which are system calls. 
>
>Clarification: the wait/wakeup between read-side and synchronize is done
>using the futex system call. There is no locking on the read-side
>per-se.
>
>Thanks,
>
>Mathieu
>
>> Those could potentially be replaced with a poll/retry system either in a 
>> different flavour of URCU or at build-time.
>> 
>> thanks,
>> kienan
>
>
>-- 
>Mathieu Desnoyers
>EfficiOS Inc.
>https://www.efficios.com