On Mon, Dec 18, 2017 at 09:41:19AM +0100, Michal Hocko wrote: > On Sat 16-12-17 23:09:25, Kirill A. Shutemov wrote: > > On Sat, Dec 16, 2017 at 12:45:25PM +0100, Michal Hocko wrote: > > > On Sat 16-12-17 04:04:10, Yang Shi wrote: > [...] > > > > Shall we add "cond_resched()" in unmap_vmas(), i.e for every 100 vmas? It > > > > may improve the responsiveness a little bit for non-preempt kernel, although > > > > it still can't release the semaphore. > > > > > > We already do, once per pmd (see zap_pmd_range). > > > > It doesn't help. We would need to find a way to drop mmap_sem, if we're > > holding it way too long. And doing it on per-vma count basis is not right > > call. It won't address issue with single huge vma. > > Absolutely agreed. I just wanted to point out that a new cond_resched is > not really needed. One way to reduce the lock starvation is to use range > locking. > > > Do we have any instrumentation that would help detect starvation on a > > rw_semaphore? > > I am afraid we don't. I guess we have enough info in mmu_gather to decide if we are doing munmap way too long. Although, getting everything right would be tricky... -- Kirill A. Shutemov -- 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>
