Windows doesn't have to write to disk if there is no memory pressure in the case of a page file but if you have an explicit file being mapped, then you'll get writes to disk. This hypothesis should be easy to observe by monitoring the disk activity during your perf tests.
From: Davies, John
Sent: 2/21/2014 1:28 PM
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] [interprocess] Shared memory object

From my reading, the Windows version is faster but it doesn’t have the persistence as the Linux version. The description mentions this:

 

A class that wraps the native Windows shared memory that is implemented as a file mapping of the paging file. Unlike shared_memory_object, windows_shared_memory has no kernel persistence and the shared memory is destroyed when all processes destroy all their windows_shared_memory objects and mapped regions for the same shared memory or the processes end/crash.

 

Boost lets you choose what means more to you.

 

 

 

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John Davies

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Email: john.davies@philips.com

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From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Patrick Steele
Sent: Thursday, February 20, 2014 11:40 AM
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] [interprocess] Shared memory object

 

Tests at the time were showing the Windows version to operate about twice as fast. If nothing has changed I guess I will remain with it then. I had just been hoping for the code to be more platform dependent.

 

On 20 February 2014 14:44, Ion Gaztañaga <igaztanaga@gmail.com> wrote:

El 20/02/2014 11:42, Patrick Steele escribió:

 

Hi,
can anyone tell me if there is a performance or other difference between
boost::interprocess::shared_memory_object and
boost::interprocess::windows_shared_memory? With the version of boost we
were using back in 2011 ( boost 1.48 ), we found that
windows_shared_memory operated faster than shared_memory_object when
transporting around 10MB of data. Is this still the case?
Thanks,

 

Nothing has changed AFAIK. shared_memory_object is a memory mapped file whereas windows_shared_memory is backed by the pagefile. I don't know why Windows should make one faster than the other, though.

Best,

Ion
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