On Thu, 9 Mar 2017 19:46:14 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > Tetsuo Handa wrote: > > This patch adds a watchdog which periodically reports number of memory > > allocating tasks, dying tasks and OOM victim tasks when some task is > > spending too long time inside __alloc_pages_slowpath(). This patch also > > serves as a hook for obtaining additional information using SystemTap > > (e.g. examine other variables using printk(), capture a crash dump by > > calling panic()) by triggering a callback only when a stall is detected. > > Ability to take administrator-controlled actions based on some threshold > > is a big advantage gained by introducing a state tracking. > > > > Commit 63f53dea0c9866e9 ("mm: warn about allocations which stall for > > too long") was a great step for reducing possibility of silent hang up > > problem caused by memory allocation stalls [1]. However, there are > > reports of long stalls (e.g. [2] is over 30 minutes!) and lockups (e.g. > > [3] is an "unable to invoke the OOM killer due to !__GFP_FS allocation" > > lockup problem) where this patch is more useful than that commit, for > > this patch can report possibly related tasks even if allocating tasks > > are unexpectedly blocked for so long. Regarding premature OOM killer > > invocation, tracepoints which can accumulate samples in short interval > > would be useful. But regarding too late to report allocation stalls, > > this patch which can capture all tasks (for reporting overall situation) > > in longer interval and act as a trigger (for accumulating short interval > > samples) would be useful. ) > Andrew, do you have any questions on this patch? > I really need this patch for finding bugs which MM people overlook. (top-posting repaired - please don't do that) Undecided. I can see the need but it is indeed quite a large lump of code. Perhaps some additional examples of how this new code was used to understand and improve real-world kernel problems would be persuasive. -- 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>