subject:"\[ros\-dev\] \[ros\-diffs\] \[tfaber\] 63953\: \[FASTFAT\] \- Do not use direct I\/O since it limits read\/write operations to 64 MB CORE\-8410 #resolve"

Re: [ros-dev] [ros-diffs] [tfaber] 63953: [FASTFAT] - Do not use direct I/O since it limits read/write operations to 64 MB CORE-8410 #resolve

2014-08-27 Thread cameron.gutman

This seems strange. I understand that NT 5.x has a limitation of 64 MB MDLs on x86, but direct I/O was designed for exactly this case of large I/O operations. Has anyone verified that 2k3 doesn’t do MDL chaining for direct I/O when the transfer is larger than a single MDL can hold? Also

Re: [ros-dev] [ros-diffs] [tfaber] 63953: [FASTFAT] - Do not use direct I/O since it limits read/write operations to 64 MB CORE-8410 #resolve

2014-08-27 Thread Thomas Faber

I've tracked down what happens on Windows in the debugger, and the relevant device objects don't have DO_DIRECT_IO set. The WDK sample FS drivers use neither I/O as well. I'm not 100% sure but from what I saw this part of our I/O manager implementation is identical to Windows's and there's no