Messages in this thread | | | Date | Fri, 31 Jul 2020 13:38:34 -0700 | From | Andrew Morton <> | Subject | Re: Raw spinlocks and memory allocation |
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On Thu, 30 Jul 2020 16:12:05 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:
> So, may we add a GFP_ flag that will cause kmalloc() and friends to return > NULL when they would otherwise need to acquire their non-raw spinlock? > This avoids adding any overhead to the slab-allocator fastpaths, but > allows callback invocation to reduce cache misses without having to > restructure some existing callers of call_rcu() and potential future > callers of kfree_rcu().
We have eight free gfp_t bits so that isn't a problem.
Adding a test-n-branch to the kmalloc() fastpath may well be a concern.
Which of mm/sl?b.c are affected?
A doesnt-need-to-really-work protopatch would help us understand the potential cost?
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