On 2014/1/22 4:41, David Rientjes wrote: > 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. > Hi David, Thanks for your kindly explanation, do you have any specific plans on this? Thanks, Jianguo Wu. > -- 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>