David Rientjes <rientjes@xxxxxxxxxx> writes: > On Tue, 9 Nov 2010, Greg Thelen wrote: > >> >> > Adding the number of swap pages to the byte limit of a memory control >> >> > group makes no sense. Convert the pages to bytes before adding them. >> >> > >> >> > The only user of this code is the OOM killer, and the way it is used >> >> > means that the error results in a higher OOM badness value. Since the >> >> > cgroup limit is the same for all tasks in the cgroup, the error should >> >> > have no practical impact at the moment. >> >> > >> >> > But let's not wait for future or changing users to trip over it. >> >> >> >> Thanks for the fix. >> >> >> > >> > Nice catch, but it's done in the opposite way: the oom killer doesn't use >> > byte limits but page limits. So this needs to be >> > >> > (res_counter_read_u64(&memcg->res, RES_LIMIT) >> PAGE_SHIFT) + >> > total_swap_pages; >> >> In -mm, the oom killer queries memcg for a byte limit using >> mem_cgroup_get_limit(). The following is from >> mem_cgroup_out_of_memory(): >> >> limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT; >> > > Oops, I missed that. I think Johannes' patch is better because > mem_cgroup_get_limit() may eventually be used elsewhere and the subsystem > has byte granularity. I have no problem with mem_cgroup_get_limit() returning a byte count as you prefer. I think this approach does have an issue. "mem_cgroup_get_limit() >> PAGE_SHIFT" may not fit within unsigned long on 32-bit machines. Does this cause a problem for the 'limit' local variable in mem_cgroup_out_of_memory(): limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT; Do we need something like the following in mem_cgroup_out_of_memory() to guard against this overflow? limit = min(mem_cgroup_get_limit(mem) >> PAGE_SHIFT, ULONG_MAX); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>