Hi all,

For a project I am doing I want to swap in/out some applications I choose. Can any one point me where is this swap in/out function in the kernel source? Is it called by the scheduling function while doing a context switching(sched.c -> schedule())?

Btw I am using Linux version 2.6.29

I don't believe Linux has used such a function since about 2.2
The "swap" partition/file is now a misnomer, and is used on a per-page, not per-process, basis.

kswapd is responsible for page migration, not the scheduler.

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Okey lets say I want to switch a process from memory. How can I do it manually by myself(not the kernel)? I mean what are the functions that needs to be called and the order of them?

I gave a printk inside the kswapd function(in mm/vmscan.c) and changed some applications but printk was printed only once upon running dmesg cmd. (I assume it was printed at the boot time, may be initialization. when I increased the application load it was not called! )

I'd hardly call this a newbie qn
Why don't you use the Report button to get the Mods to move it to the Programming forum; I think you'll get the help you need better over there.

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Thanks for the suggestion

Moved: This thread is more suitable in <PROGRAMMING> and has been moved accordingly to help your thread/question get the exposure it deserves.

You can't. As far as I know, there is no kernel module providing that facility.

In a large majority of cases, the user decision on what to swap, would most likely be wrong anyway. Only the kernel has the requisite information on what memory has been accessed recently, to make efficient swapping decisions.

That said, you can always increase swappiness so that the kernel is more aggressive in swapping out unneeded pages.

If you wanted to create such a facility, you would have to write a kernel module. Note that for the above reasons, you would need very good reasons why this would be useful, in order to get your module accepted upstream. That kernel module would then provide some kind of an interface, perhaps a PID list written to a /sys file. The module would scan the processes for all pages owned by them, and attempt to swap them all out. (You might wish to skip shared mappings, so other processes using e.g. the same libraries won't be affected.)

Because I for one fail to see the usefulness of such a kernel module, I haven't checked the kernel sources to see which interfaces would be useful for this.

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My sentiments as well. The whole concept of process swap went out of fashion years ago. In all (normal) environments I'm aware of.

However, were I of such a mind, maybe I'd start by looking at the hibernation code for some ideas. Having sat in on some sessions from the folks during the development of what is now known as TuxOnIce, it was apparently a minefield.

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