On Tue 30-01-18 10:00:07, Christian König wrote: > Am 30.01.2018 um 08:55 schrieb Michal Hocko: > > On Tue 30-01-18 02:56:51, He, Roger wrote: > > > Hi Michal: > > > > > > We need a API to tell TTM module the system totally has how many swap > > > cache. Then TTM module can use it to restrict how many the swap cache > > > it can use to prevent triggering OOM. For Now we set the threshold of > > > swap size TTM used as 1/2 * total size and leave the rest for others > > > use. > > Why do you so much memory? Are you going to use TB of memory on large > > systems? What about memory hotplug when the memory is added/released? > > For graphics and compute applications on GPUs it isn't unusual to use large > amounts of system memory. > > Our standard policy in TTM is to allow 50% of system memory to be pinned for > use with GPUs (the hardware can't do page faults). > > When that limit is exceeded (or the shrinker callbacks tell us to make room) > we wait for any GPU work to finish and copy buffer content into a shmem > file. > > This copy into a shmem file can easily trigger the OOM killer if there isn't > any swap space left and that is something we want to avoid. > > So what we want to do is to apply this 50% rule to swap space as well and > deny allocation of buffer objects when it is exceeded. How does that help when the rest of the system might eat swap? > > > But get_nr_swap_pages is the only API we can accessed from other > > > module now. It can't cover the case of the dynamic swap size > > > increment. I mean: user can use "swapon" to enable new swap file or > > > swap disk dynamically or "swapoff" to disable swap space. > > Exactly. Your scaling configuration based on get_nr_swap_pages or the > > available memory simply sounds wrong. > > Why? That is pretty much exactly what we are doing with buffer objects and > system memory for years. Could you be more specific? What kind of buffer objects you have in mind? -- Michal Hocko SUSE Labs -- 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>
