Re: [RFC PATCH for 4.18 12/23] cpu_opv: Provide cpu_opv system call (v7)
- Date: Thu, 12 Apr 2018 13:07:15 -0700
- From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
- Subject: Re: [RFC PATCH for 4.18 12/23] cpu_opv: Provide cpu_opv system call (v7)
On Thu, Apr 12, 2018 at 12:59 PM, Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > > What are your concerns about page pinning ? Pretty much everything. It's the most complex part by far, and the vmalloc space is a limited resource on 32-bit architectures. > Do you have an alternative approach in mind ? Do everything in user space. And even if you absolutely want cpu_opv at all, why not do it in the user space *mapping* without the aliasing into kernel space? The cpu_opv approach isn't even fast. It's *really* slow if it has to do VM crap. The whole rseq thing was billed as "faster than atomics". I *guarantee* that the cpu_opv's aren't faster than atomics. Linus
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