Re: [PATCH v8 1/9] dax: Use percpu rwsem for dax_{read,write}_lock()
From: Shiyang Ruan <hidden>
Date: 2021-12-15 02:06:37
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linux-fsdevel, linux-xfs, lkml, nvdimm
在 2021/12/14 23:40, Christoph Hellwig 写道:
On Thu, Dec 02, 2021 at 04:48:48PM +0800, Shiyang Ruan wrote:quoted
In order to introduce dax holder registration, we need a write lock for dax. Change the current lock to percpu_rw_semaphore and introduce a write lock for registration.Why do we need to change the existing, global locking for that?
I think we have talked about this in the previous v7 patchset: https://lore.kernel.org/nvdimm/20210924130959.2695749-1-ruansy.fnst@fujitsu.com/T/#m4031bc3dc49dcbaac6f8d99877f910fa9a6f998a (local) If it is a global lock, any write lock will block other dax devices.
What is the impact of this to benchmarks? Also if we stop using srcu protection, we should be able to get rid of grace periods or RCU frees.
I didn't test in benchmarks for now. Could you show me which one I should test this code on? I am not familiar with this... -- Thanks, Ruan.