On Thursday 15 December 2005 19:55, Kyle Moffett wrote: > On Dec 15, 2005, at 03:21, David S. Miller wrote: > > Not when we run out, but rather when we reach some low water mark, > > the "critical sockets" would still use GFP_ATOMIC memory but only > > "critical sockets" would be allowed to do so. > > > > But even this has faults, consider the IPSEC scenerio I mentioned, > > and this applies to any kind of encapsulation actually, even simple > > tunneling examples can be concocted which make the "critical > > socket" idea fail. > > > > The knee jerk reaction is "mark IPSEC's sockets critical, and mark > > the tunneling allocations critical, and... and..." well you have > > GFP_ATOMIC then my friend. > > > > In short, these "seperate page pool" and "critical socket" ideas do > > not work and we need a different solution, I'm sorry folks spent so > > much time on them, but they are heavily flawed. > > What we really need in the kernel is a more fine-grained memory > priority system with PI, similar in concept to what's being done to > the scheduler in some of the RT patchsets. Currently we have a very > black-and-white memory subsystem; when we go OOM, we just start > killing processes until we are no longer OOM. Perhaps we should have > some way to pass memory allocation priorities throughout the kernel, > including a "this request has X priority", "this request will help > free up X pages of RAM", and "drop while dirty under certain OOM to > free X memory using this method". > > The initial benefit would be that OOM handling would become more > reliable and less of a special case. When we start to run low on > free pages, it might be OK to kill the [EMAIL PROTECTED] process long before > we OOM if such action might prevent the OOM. Likewise, you might be > able to flag certain file pages as being "less critical", such that > the kernel can kill a process and drop its dirty pages for files in / > tmp. Or the kernel might do a variety of other things just by > failing new allocations with low priority and forcing existing > allocations with low priority to go away using preregistered handlers. > > When processes request memory through any subsystem, their memory > priority would be passed through the kernel layers to the allocator, > along with any associated information about how to free the memory in > a low-memory condition. As a result, I could configure my database > to have a much higher priority than [EMAIL PROTECTED] (or boinc or whatever), > so that when the database server wants to fill memory with clean DB > cache pages, the kernel will kill [EMAIL PROTECTED] for it's memory, even if > we could just leave some DB cache pages unfaulted. > > Questions? Comments? "This is a terrible idea that should never have > seen the light of day"? Both constructive and destructive criticism > welcomed! (Just please keep the language clean! :-D)
I have some basic process-that-called the memory allocator link in the -ck tree already which alters how aggressively memory is reclaimed according to priority. It does not affect out of memory management but that could be added to said algorithm; however I don't see much point at the moment since oom is still an uncommon condition but regular memory allocation is routine. Cheers, Con - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
