> On Wed 20-01-21 17:21:46, Uladzislau Rezki (Sony) wrote: > > For a single argument we can directly request a page from a caller > > context when a "carry page block" is run out of free spots. Instead > > of hitting a slow path we can request an extra page by demand and > > proceed with a fast path. > > > > A single-argument kvfree_rcu() must be invoked in sleepable contexts, > > and that its fallback is the relatively high latency synchronize_rcu(). > > Single-argument kvfree_rcu() therefore uses GFP_KERNEL|__GFP_RETRY_MAYFAIL > > to allow limited sleeping within the memory allocator. > > __GFP_RETRY_MAYFAIL can be quite heavy. It is effectively the most heavy > way to allocate without triggering the OOM killer. Is this really what > you need/want? Is __GFP_NORETRY too weak? > Hm... We agreed to proceed with limited lightwait memory direct reclaim. Johannes Weiner proposed to go with __GFP_NORETRY flag as a starting point: https://www.spinics.net/lists/rcu/msg02856.html <snip> So I'm inclined to suggest __GFP_NORETRY as a starting point, and make further decisions based on instrumentation of the success rates of these opportunistic allocations. <snip> but for some reason, i can't find a tail or head of it, we introduced __GFP_RETRY_MAYFAIL what is a heavy one from a time consuming point of view. What we would like to avoid. I tend to say that it was a typo. Thank you for pointing to it! -- Vlad Rezki
