Hello, Andrew. On Thu, Jul 31, 2014 at 06:16:56PM -0700, Andrew Morton wrote: > Yet nowhere in either the changelog or the code comments is it even > mentioned that this allocator is unreliable and that callers *must* > implement (and test!) fallback paths.
Hmmm, yeah, somehow the atomic behavior seemed obvious to me. I'll try to make it clear that this thing can and does fail. > > an obvious solution is adding a failure > > injection for debugging, but really except for being a bit ghetto, > > this is just the atomic allocation for percpu areas. > > If it was a try-GFP_ATOMIC-then-fall-back-to-pool thing then it would > work fairly well. But it's not even that - a caller could trivially > chew through that pool in a single timeslice. Especially on !SMP. > Especially squared with !PREEMPT or SCHED_FIFO. Yeap, occassional pool depletion would be a normal thing to happen, which isn't a correctness issue and most likely not even a performance issue. > But please make very sure that this is how we position it. I don't > know how to do this. Maybe prefix the names with "blk_" to signify > that it is block-private (and won't even be there if !CONFIG_BLOCK). > > Or rename percpu_pool_alloc() to percpu_pool_try_alloc() - that should > wake people up. Sounds good to me. I'll rename it to percpu_pool_try_alloc() and make it clear in the comment that the allocation is opportunistic. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
