Messages in this thread | | | Date | Mon, 20 Nov 2017 10:28:38 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock. |
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On Mon, Nov 20, 2017 at 07:56:28PM +0900, Tetsuo Handa wrote: > Christoph Hellwig wrote: > > On Mon, Nov 20, 2017 at 10:42:37AM +0100, Michal Hocko wrote: > > > The patch has been dropped because allnoconfig failed to compile back > > > then http://lkml.kernel.org/r/CAP=VYLr0rPWi1aeuk4w1On9CYRNmnEWwJgGtaX=wEvGaBURtrg@mail.gmail.com > > > I have problem to find the follow up discussion though. The main > > > argument was that SRC is not generally available and so the core > > > kernel should rely on it. > > > > Paul, > > > > isthere any good reason to not use SRCU in the core kernel and > > instead try to reimplement it using atomic counters? > > CONFIG_SRCU was added in order to save system size. There are users who run Linux on very > small systems ( https://www.elinux.org/images/5/52/Status-of-embedded-Linux-2017-09-JJ62.pdf ). > > Also, atomic counters are not mandatory for shrinker case; e.g. > http://lkml.kernel.org/r/201711161956.EBF57883.QFFMOLOVSOHJFt@I-love.SAKURA.ne.jp .
CONFIG_SRCU was indeed added in order to shrink single-CPU systems. But many architectures are now requiring SRCU for one reason or another, in more and more situations.
So I recently implemented a UP-only Tiny SRCU, which is quite a bit smaller than its scalable counterpart, Tree SRCU:
text data bss dec hex filename 983 64 0 1047 417 /tmp/c/kernel/rcu/srcutiny.o
text data bss dec hex filename 6844 193 0 7037 1b7d /tmp/b/kernel/rcu/srcutree.o
So perhaps it is time to unconditionally enable SRCU?
Thanx, Paul
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