Re: [PATCH v2 6/8] mm/lru: remove rcu_read_lock to fix performance regression

Alex Shi
2019-11-13T02:40:58Z

ÔÚ 2019/11/12 ÏÂÎç10:38, Matthew Wilcox Ð´µÀ:
> On Tue, Nov 12, 2019 at 10:06:26PM +0800, Alex Shi wrote:
>> Intel 0day report there are performance regression on this patchset.
>> The detailed info points to rcu_read_lock + PROVE_LOCKING which causes
>> queued_spin_lock_slowpath waiting too long time to get lock.
>> Remove rcu_read_lock is safe here since we had a spinlock hold.
> Argh. You have not sent these patches in a properly reviewable form!
> I wasted all that time reviewing the earlier patch in this series only to
> find out that you changed it here. FIX THE PATCH, don't send a fix-patch
> on top of it!
>

Hi Matthew,

Very sorry for your time! The main reasons I use a separate patch since a, Intel 0day asking me to credit their are founding, and I don't know how to give a clearly/elegant explanation for a non-exist regression in a fixed patch. b, this regression is kindly pretty tricky. Maybe it's better saying thanks in version change log of cover-letter?

Anyway, Thanks a lot for your review!

Alex