On Tue, 21 Jan 2014, Jianguo Wu wrote: > > The problem is that slabinfo becomes excessively verbose and dumping it > > all to the kernel log often times causes important messages to be lost. > > This is why we control things like the tasklist dump with a VM sysctl. It > > would be possible to dump, say, the top ten slab caches with the highest > > memory usage, but it will only be helpful for slab leaks. Typically there > > are better debugging tools available than analyzing the kernel log; if you > > see unusually high slab memory in the meminfo dump, you can enable it. > > > > But, when OOM has happened, we can only use kernel log, slab/vmalloc info from proc > is stale. Maybe we can dump slab/vmalloc with a VM sysctl, and only top 10/20 entrys? > You could, but it's a tradeoff between how much to dump to a general resource such as the kernel log and how many sysctls we add that control every possible thing. Slab leaks would definitely be a minority of oom conditions and you should normally be able to reproduce them by running the same workload; just use slabtop(1) or manually inspect /proc/slabinfo while such a workload is running for indicators. I don't think we want to add the information by default, though, nor do we want to add sysctls to control the behavior (you'd still need to reproduce the issue after enabling it). We are currently discussing userspace oom handlers, though, that would allow you to run a process that would be notified and allowed to allocate a small amount of memory on oom conditions. It would then be trivial to dump any information you feel pertinent in userspace prior to killing something. I like to inspect heap profiles for memory hogs while debugging our malloc() issues, for example, and you could look more closely at kernel memory. I'll cc you on future discussions of that feature. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>