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fork: Optimize task creation by caching two thread stacks per CPU if …
…CONFIG_VMAP_STACK=y vmalloc() is a bit slow, and pounding vmalloc()/vfree() will eventually force a global TLB flush. To reduce pressure on them, if CONFIG_VMAP_STACK=y, cache two thread stacks per CPU. This will let us quickly allocate a hopefully cache-hot, TLB-hot stack under heavy forking workloads (shell script style). On my silly pthread_create() benchmark, it saves about 2 µs per pthread_create()+join() with CONFIG_VMAP_STACK=y. Signed-off-by: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Jann Horn <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/94811d8e3994b2e962f88866290017d498eb069c.1474003868.git.luto@kernel.org Signed-off-by: Ingo Molnar <[email protected]>
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