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Subject: Re: [PATCH RFC v2 02/10] mm: Make shrink_slab() lockless
To:     Kirill Tkhai <ktkhai@virtuozzo.com>
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Date:   Thu, 9 Aug 2018 19:37:32 +0900
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On 2018/08/09 18:21, Kirill Tkhai wrote:
> 2)SRCU. Pros are there are no the above problems; we will have completely unlocked and
>   scalable shrink_slab(). We will also have a possibility to avoid unregistering delays,
>   like I did for superblock shrinker. There will be full scalability.
>   Cons is enabling SRCU.
> 

How unregistering delays can be avoided? Since you traverse all shrinkers
using one shrinker_srcu, synchronize_srcu(&shrinker_srcu) will block
unregistering threads until longest inflight srcu_read_lock() user calls
srcu_read_unlock().

Unless you use per shrinker counter like below, I wonder whether
unregistering delays can be avoided...

  https://marc.info/?l=linux-mm&m=151060909613004
  https://marc.info/?l=linux-mm&m=151060909713005