Messages in this thread | | | Date | Mon, 7 Oct 2019 07:16:51 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature |
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Hello,
On Wed, Oct 02, 2019 at 03:28:00PM +0900, Namhyung Kim wrote: > On Sat, Sep 21, 2019 at 6:04 AM Tejun Heo <tj@kernel.org> wrote: > > > > On Fri, Sep 20, 2019 at 05:47:45PM +0900, Namhyung Kim wrote: > > > Thanks for the sharing information! For 32-bit, while the ino itself is not > > > monotonic, gen << 32 + ino is monotonic right? I think we can use the > > > > It's not. gen gets incremented on every allocation, so it has not > > high but still realistic chance of collisions. > > In __kernfs_new_node(), gen gets increased only if idr_alloc_cyclic() > returns lower than the cursor... I'm not sure you talked about it.
Ah, I forgot that it's using cyclic idr, so yeah, it's not as bad in terms of recycling although cyclic allocation on idr is pretty inefficient. I still think it'd be better to switch to rbtree and so that 64bit can simply use monotonically increasing numbers but that definitely isn't a must and we can juse continue with the current allocation method.
Thanks.
-- tejun
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