Messages in this thread | | | Date | Wed, 6 Sep 2023 20:27:41 +0900 | From | Bongkyu Kim <> | Subject | Re: [PATCH v2 1/2] Revert "locking/rwsem: Remove reader optimistic spinning" |
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On Mon, Sep 04, 2023 at 03:56:56PM -0400, Waiman Long wrote: > On 9/4/23 11:10, Peter Zijlstra wrote: > > On Fri, Sep 01, 2023 at 10:07:03AM +0900, Bongkyu Kim wrote: > > > This reverts commit 617f3ef95177840c77f59c2aec1029d27d5547d6. > > > > > > In mobile environment, reader optimistic spinning is still useful > > > because there're not many readers. In my test result at android device, > > > it improves application startup time about 3.8% > > > App startup time is most important factor for android user expriences. > > > So, re-enable reader optimistic spinning by this commit. And, > > > the later patch will make it optional feature by cmdline. > > I'm not seeing any mention on how this interacts with all the rwsem work > > that has been done since that commit, like the handoff rework. > > > > Why is a straight revert a sane thing at this point? > > I also agree that a revert is not the best way to reintroduce the feature. > It should document the reason why reader optimistic spinning is not the > default as discussed in commit 617f3ef9517 ("locking/rwsem: Remove reader > optimistic spinning") and under what condition should reader optimistic > spinning can be turned back on. > > Besides, I now think we may not really need 2 separate nonspinnable bits. We > can go with one that is set by writer timing out when spinning on reader. > > Cheers, > Longman
Should I modify like the below? - Title to "locking/rwsem: Reintroduce reader optimistic spinning" - Add more document like Longman's comment - Reconsidering about 2 separate nonspinnable bits to one
Thanks, Bongkyu
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