On Wed, Nov 27, 2013 at 04:22:18PM -0800, David Rientjes wrote: > On Wed, 27 Nov 2013, Johannes Weiner wrote: > > > > The patch is drawing the line at "the kernel can no longer do anything to > > > free memory", and that's the line where userspace should be notified or a > > > process killed by the kernel. > > > > > > Giving current access to memory reserves in the oom killer is an > > > optimization so that all reclaim is exhausted prior to declaring > > > that they are necessary, the kernel still has the ability to allow > > > that process to exit and free memory. > > > > "they" are necessary? > > > > Memory reserves. > > > > This is the same as the oom notifiers within the kernel that free > > > memory from s390 and powerpc archs: the kernel still has the ability > > > to free memory. > > > > They're not the same at all. One is the kernel freeing memory, the > > other is a random coincidence. > > > > Current is on the way to memory freeing because it has a pending SIGKILL > or is already exiting, it simply needs access to memory reserves to do so. > This was originally introduced to prevent the oom killer from having to > scan the set of eligible processes and silently giving it access to memory > reserves; we didn't want to emit all of the messages to the kernel log > because scripts (and admins) were looking at the kernel log and seeing > that the oom killer killed something when it really came from a different > source or was already exiting. > > We have a differing opinion on what to consider the point of oom (the > "notification line that has to be drawn"). My position is to notify > userspace when the kernel has exhausted its capability to free memory > without killing something. In the case of current exiting or having a > pending SIGKILL, memory is going to be freed, the oom killer simply needs > to preempt the tasklist scan. The situation is going to be remedied. I > defined the notification with this patch to only happen when the kernel > can't free any memory without a kill so that userspace may do so itself. > Michal concurred with that position. The long-standing, user-visible definition of the current line agrees with me. You can't just redefine this, period. I tried to explain to you how insane the motivation for this patch is, but it does not look like you are reading what I write. But you don't get to change user-visible behavior just like that anyway, much less so without a sane reason, so this was a complete waste of time :-( -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
