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Subject: Re: Restartable Sequences system call merged into Linux
To: Pavel Machek <pavel@ucw.cz>,
 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: carlos <carlos@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
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 Boqun Feng <boqun.feng@gmail.com>, Thomas Gleixner <tglx@linutronix.de>,
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From: Florian Weimer <fweimer@redhat.com>
Message-ID: <48a0d905-2568-51b8-80c9-a20ecaa25f9b@redhat.com>
Date: Thu, 14 Jun 2018 14:01:00 -0000
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On 06/14/2018 03:49 PM, Pavel Machek wrote:
> Hi!
> 
>>>> - rseq_preempt(): on preemption, the scheduler sets the TIF_NOTIFY_RESUME thread
>>>>    flag, so rseq_handle_notify_resume() can check whether it's in a rseq critical
>>>>    section when returning to user-space,
>>>> - rseq_signal_deliver(): on signal delivery, rseq_handle_notify_resume() checks
>>>>    whether it's in a rseq critical section,
>>>> - rseq_migrate: on migration, the scheduler sets TIF_NOTIFY_RESUME as well,
>>>
>>> Yes, this is not likely to be noticeable.
>>>
>>> But the proposal wanted to add a syscall to thread creation, right?
>>> And I believe that may be noticeable.
>>
>> Fair point! Do we have a standard benchmark that would stress this ?
> 
> Web server performance benchmarks basically test clone() performance
> in many cases.

Isn't that fork?  I expect that the rseq arena is inherited on fork and 
fork-type clone, otherwise it's going to be painful.

Thanks,
Florian