On Mon, Jan 7, 2019 at 10:04 AM Manfred Spraul <manf...@colorfullife.com> wrote: > > On 1/3/19 11:18 PM, Shakeel Butt wrote: > > Hi Manfred, > > > > On Sun, Dec 23, 2018 at 4:26 AM Manfred Spraul > > <manf...@colorfullife.com> wrote: > >> Hello Dmitry, > >> > >> On 12/23/18 10:57 AM, Dmitry Vyukov wrote: > >>> I can reproduce this infinite memory consumption with the C > >>> program: > >>> https://gist.githubusercontent.com/dvyukov/03ec54b3429ade16fa07bf8b2379aff3/raw/ae4f654e279810de2505e8fa41b73dc1d77778e6/gistfile1.txt > >>> > >>> But this is working as intended, right? It just creates infinite > >>> number of large semaphore sets, which reasonably consumes infinite > >>> amount of memory. > >>> Except that it also violates the memcg bound and a process can > >>> have > >>> effectively unlimited amount of such "drum memory" in semaphores. > >> Yes, this is as intended: > >> > >> If you call semget(), then you can use memory, up to the limits in > >> /proc/sys/kernel/sem. > >> > >> Memcg is not taken into account, an admin must set > >> /proc/sys/kernel/sem. > >> > >> The default are "infinite amount of memory allowed", as this is the > >> most > >> sane default: We had a logic that tried to autotune (i.e.: a new > >> namespace "inherits" a fraction of the parent namespaces memory > >> limits), > >> but this we more or less always wrong. > >> > >> > > What's the disadvantage of setting the limits in > > /proc/sys/kernel/sem > > high and let the task's memcg limits the number of semaphore a > > process > > can create? Please note that the memory underlying shmget and msgget > > is already accounted to memcg. > > Nothing, it it just a question of implementing it. >
I think it should be something like following: --- ipc/sem.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 745dc6187e84..ad63df2658aa 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -494,7 +494,7 @@ static struct sem_array *sem_alloc(size_t nsems) return NULL; size = sizeof(*sma) + nsems * sizeof(sma->sems[0]); - sma = kvmalloc(size, GFP_KERNEL); + sma = kvmalloc(size, GFP_KERNEL_ACCOUNT); if (unlikely(!sma)) return NULL; @@ -1897,7 +1897,8 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) rcu_read_unlock(); /* step 2: allocate new undo structure */ - new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); + new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, + GFP_KERNEL_ACCOUNT); if (!new) { ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); return ERR_PTR(-ENOMEM); -- 2.20.1.97.g81188d93c3-goog