On Tue, Jun 28, 2016 at 06:37:24PM +0800, Chen Feng wrote: > Thanks for you reply. > > On 2016/6/28 0:57, Vladimir Davydov wrote: > > On Mon, Jun 27, 2016 at 07:02:15PM +0800, Chen Feng wrote: > >> In my platform, there can be cache a lot of memory in > >> ion page pool. When shrink memory the nr_to_scan to ion > >> is always to little. > >> to_scan: 395 ion_pool_cached: 27305 > > > > That's OK. We want to shrink slabs gradually, not all at once. > > > > OK， But my question there are a lot of memory waiting for free. > But the to_scan is too little. Small value of 'total_scan' in comparison to 'freeable' (in shrink_slab) means that memory pressure is not really high and so there's no need to scan all cached objects yet. > > So, the lowmemorykill may kill the wrong process. > >> > >> Currently, the shrinker nr_deferred is set to total_scan. > >> But it's not the real left of the shrinker. > > > > And it shouldn't. The idea behind nr_deferred is following. A shrinker > > may return SHRINK_STOP if the current allocation context doesn't allow > > to reclaim its objects (e.g. reclaiming inodes under GFP_NOFS is > > deadlock prone). In this case we can't call the shrinker right now, but > > if we just forget about the batch we are supposed to reclaim at the > > current iteration, we can wind up having too many of these objects so > > that they start to exert unfairly high pressure on user memory. So we > > add the amount that we wanted to scan but couldn't to nr_deferred, so > > that we can catch up when we get to shrink_slab() with a proper context. > > > I am confused with your comments. If the shrinker return STOP this time. > It also can return STOP next time. There's always kswapd running in background which calls reclaim with GFP_KERNEL. So even if a process issues a lot of successive GFP_NOFS, which makes fs shrinkers abort scan, their objects will still be scanned and reclaimed by kswapd. -- 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>