On 2014/1/21 13:34, David Rientjes wrote: > On Mon, 20 Jan 2014, Jianguo Wu wrote: > >> When OOM happen, will dump buddy free areas info, hugetlb pages info, >> memory state of all eligible tasks, per-cpu memory info. >> But do not dump slab/vmalloc info, sometime, it's not enough to figure out the >> reason OOM happened. >> >> So, my questions are: >> 1. Should dump slab/vmalloc info when OOM happen? Though we can get these from proc file, >> but usually we do not monitor the logs and check proc file immediately when OOM happened. >> > Hi David, Thank you for your patience to answer! > 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? Thanks. >> 2. /proc/$pid/smaps and pagecache info also helpful when OOM, should also be dumped? >> > > Also very verbose and would cause important messages to be lost, we try to > avoid spamming the kernel log with all of this information as much as > possible. > >> 3. Without these info, usually how to figure out OOM reason? >> > > Analyze the memory usage in the meminfo and determine what is unusually > high; if it's mostly anonymous memory, you can usually correlate it back > to a high rss for a process in the tasklist that you didn't suspect to be > using that much memory, for example. > > -- 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>