On Tue, 15 Nov 2011 07:41:54 +0100 Andrew Shadura <bugzilla@tut.by> wrote: > Hello, > > On Mon, 14 Nov 2011 00:14:18 +0100 > Josselin Mouette <joss@debian.org> wrote: > > > > No it does not work like you said. We know the matrix structure, not > > > the kernel. We map and unmap manually. Doing as you said is > > > inneficient and trash a lot cache and so on. > > > This is getting insane. Please learn how to use madvise and > > posix_fadvise and let the kernel deal with paging. The kernel knows > > everything about the underlying hardware; the application does not. > > And what about the software being cross-platform? What about other > systems which don't have such system calls? Ever heard of #ifdef #else #endif ? If similar calls exist, use them conditionally. Where they do not exist, you need to decide if that system can be supported and accept the limitations of doing so. Where the calls DO exist it is inexcusable NOT to use the support available. Do not cripple all platforms with the sins of the weakest. > Also, the application > doesn't need to know anything about the hardware except that disk > memory is usually larger and slower than RAM is. For a trivial application, that is true. For any application which makes specific or unusual demands on the hardware / system resources, it is not. Applications making specific or unusual demands MUST allow for system differences and that includes adjusting to those which can handle the requests *better* than your own code as well as providing code for (or preventing a build / deployment on) those which cannot. Some kinds of applications just cannot avoid a direct interface with the kernel (anything using iptables, for example) and any process which makes unusual demands on the available temporary storage is certainly sufficiently specialised to require conditionals in the code which make use of kernel features where those are available. Cross-platform is not an excuse for one-class-for-all. Cross-platform means making the most of each platform, not dumbing down to the lowest, meanest or most inept. If you want compile-once run anywhere, you could try java and move all these problems to the VM. (Which has to do this system-specific stuff anyway.) If the application needs to be recompiled to be cross-platform then there is absolutely NO EXCUSE for not including conditional compilation for specific kernels or environments. Your build system is unquestionably doing some adjustments from one platform to another anyway - you simply have to bring those conditionals into the codebase. There is no excuse - your software is broken and it must be fixed or removed. (and, yes, I've explicitly included iptables as an example because I've got an RC bug outstanding for a tiny app which cannot therefore be used on BSD and I keep meaning to find the time to fix the build requirements, so this is directed at me as much as anyone else.) -- Neil Williams ============= http://www.linux.codehelp.co.uk/
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