Messages in this thread | | | Subject | Re: [PATCH v2 0/3] staging: zcache: xcfmalloc support | From | Dave Hansen <> | Date | Mon, 03 Oct 2011 11:22:34 -0700 |
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On Mon, 2011-10-03 at 13:54 -0400, Nitin Gupta wrote: > I think disabling preemption on the local CPU is the cheapest we can get > to protect PCPU buffers. We may experiment with, say, multiple buffers > per CPU, so we end up disabling preemption only in highly improbable > case of getting preempted just too many times exactly within critical > section.
I guess the problem is two-fold: preempt_disable() and local_irq_save().
> static int zcache_put_page(int cli_id, int pool_id, struct tmem_oid *oidp, > uint32_t index, struct page *page) > { > struct tmem_pool *pool; > int ret = -1; > > BUG_ON(!irqs_disabled());
That tells me "zcache" doesn't work with interrupts on. It seems like awfully high-level code to have interrupts disabled. The core page allocator has some irq-disabling spinlock calls, but that's only really because it has to be able to service page allocations from interrupts. What's the high-level reason for zcache?
I'll save the discussion about preempt for when Seth posts his patch.
-- Dave
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