Re: swapping of mod_perl parent process / mlockall()
On Mon, 16 Jul 2001, Adi Fairbank wrote: Actually, I don't want child processes to inherit the page locks across a fork. I just wanted to experiment with performance issues when only the parent process is locked in memory. (I have a theory that when the parent process swaps to disk, the swapped pages become unshared for the rest of the server's life) I was hoping you could give me a hint as to where in the source code I could call mlockall(), e.g. file mod_perl.c, line NNN.. you should just be able to create a module with a .xs something like: #include EXTERN.h #include perl.h #include XSUB.h #include sys/mman.h MODULE = Mlock PACKAGE = Mlock int mlockall() CODE: RETVAL = (mlockall(MCL_CURRENT) == 0); OUTPUT: RETVAL and call Mlock::mlockall(); in a startup script.
Re: swapping of mod_perl parent process / mlockall()
Doug MacEachern wrote: On Tue, 26 Jun 2001, Adi Fairbank wrote: If this is the case, it would be helpful to prevent the parent process from *ever* swapping to disk. The Linux kernel has a system call mlockall() which disables all memory paging for the current process. This sounds like exactly the recipe for preventing parent process swapping. It won't affect spawned child processes, so shouldn't pose a threat of consuming all physical memory and crashing the system. I want to play around with this, but I'm not sure where in the mod_perl source to call mlockall(). It would need to be before the parent spawns any children.. Has anyone tried using Linux's mlockall()/mlock() with mod_perl? according the manpage: Child processes do not inherit page locks across a fork. so you would need to call it in a child init handler, but: Only root processes are allowed to lock pages. Actually, I don't want child processes to inherit the page locks across a fork. I just wanted to experiment with performance issues when only the parent process is locked in memory. (I have a theory that when the parent process swaps to disk, the swapped pages become unshared for the rest of the server's life) I was hoping you could give me a hint as to where in the source code I could call mlockall(), e.g. file mod_perl.c, line NNN.. Thanks, -Adi
Re: swapping of mod_perl parent process / mlockall()
On Tue, 26 Jun 2001, Adi Fairbank wrote: Is it correct that when the Apache/mod_perl parent process swaps to disk, a large part of it (swapped pages) becomes unshared? Even after the kernel restores the pages from swap, do they remain unshared? So once the parent process becomes unshared, new apache children that are spawned only share the parent's pages that have never been swapped? This is what I've grok'ed from my experiments with top/GTop. If this is the case, it would be helpful to prevent the parent process from *ever* swapping to disk. The Linux kernel has a system call mlockall() which disables all memory paging for the current process. This sounds like exactly the recipe for preventing parent process swapping. It won't affect spawned child processes, so shouldn't pose a threat of consuming all physical memory and crashing the system. I want to play around with this, but I'm not sure where in the mod_perl source to call mlockall(). It would need to be before the parent spawns any children.. Has anyone tried using Linux's mlockall()/mlock() with mod_perl? according the manpage: Child processes do not inherit page locks across a fork. so you would need to call it in a child init handler, but: Only root processes are allowed to lock pages.
