lkml.org 
[lkml]   [2017]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 2/9] slab: remove synchronous rcu_barrier() call in memcg cache release path
    Hello, Vladimir.

    On Sat, Jan 14, 2017 at 04:19:39PM +0300, Vladimir Davydov wrote:
    > On Sat, Jan 14, 2017 at 12:54:42AM -0500, Tejun Heo wrote:
    > > This patch updates the cache release path so that it simply uses
    > > call_rcu() instead of the synchronous rcu_barrier() + custom batching.
    > > This doesn't cost more while being logically simpler and way more
    > > scalable.
    >
    > The point of rcu_barrier() is to wait until all rcu calls freeing slabs
    > from the cache being destroyed are over (rcu_free_slab, kmem_rcu_free).
    > I'm not sure if call_rcu() guarantees that for all rcu implementations
    > too. If it did, why would we need rcu_barrier() at all?

    Yeah, I had a similar question and scanned its users briefly. Looks
    like it's used in combination with ctors so that its users can
    opportunistically dereference objects and e.g. check ids / state /
    whatever without worrying about the objects' lifetimes.

    Thanks.

    --
    tejun

    \
     
     \ /
      Last update: 2017-01-14 16:20    [W:3.053 / U:0.024 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site