Messages in this thread | | | Subject | Re: [PATCH] xfs: optimise xfs_mod_icount/ifree when delta < 0 | From | Shaokun Zhang <> | Date | Tue, 5 Nov 2019 11:08:01 +0800 |
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Hi Christoph,
On 2019/11/4 23:25, Christoph Hellwig wrote: > On Mon, Nov 04, 2019 at 07:29:40PM +0800, Shaokun Zhang wrote: >> From: Yang Guo <guoyang2@huawei.com> >> >> percpu_counter_compare will be called by xfs_mod_icount/ifree to check >> whether the counter less than 0 and it is a expensive function. >> let's check it only when delta < 0, it will be good for xfs's performance. > > How much overhead do you see? In the end the compare is just a debug
Thanks your reply, sorry for my not clear description. __percpu_counter_compare itself is not expensive, but __percpu_counter_sum called by __percpu_counter_compare is high load, I will list it in next thread.
> check, so if it actually shows up we should remove it entirely. >
I'm not sure about it, so I check the delta to do less modification.
Thanks, Shaokun
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