Re: [boost] Serialisation: Is is_trivial<T> a sufficient precondition to bypass serialisation?

Subject: Re: [boost] Serialisation: Is is_trivial<T> a sufficient precondition to bypass serialisation?
From: Olaf van der Spek (ml_at_[hidden])
Date: 2015-02-06 07:52:55

On Fri, Feb 6, 2015 at 1:20 PM, Niall Douglas <s_sourceforge_at_[hidden]> wrote:
> On 6 Feb 2015 at 11:07, Mathias Gaunard wrote:
>
>> > As with network sockets, most DMA engines for disk i/o have hard
>> > limits on scatter gather buffer size. That isn't AFIO's problem.
>>
>> So if I try to write a std::vector that is too large to fit in a
>> scatter/gather buffer, my write will fail?
>
> AFIO observes the IOV_MAX batch limit, so on POSIX with pwritev()
> support no it should never fail, though of course you lose atomicity
> between IOV_MAX batches. On POSIX without pwritev() support AFIO
> issues each buffer singly anyway, so your atomicity is per buffer.
>
> On Windows if buffered i/o is on then there is no limit and atomicity
> is per buffer (Windows has no scatter gather file i/o functions for
> buffered files). If buffered i/o is off, the WriteFileGather() API
> currently has an unofficial limit of 32Mb on x64 operating systems
> due to NT kernel structure limits. Because this limit is not
> documented and not stable even across 32 bit vs 64 bit systems never
> mind between Intel and ARM, AFIO passes through your request as-is,
> and returns an error if the WriteFileGather() API does.

What's the definition of atomicity here?

-- 
Olaf