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Harding" , Andrew Morton , Pekka Enberg , Matthew Wilcox , Tycho Andersen , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC 02/15] slub: Add isolate() and migrate() methods In-Reply-To: <20190311215106.GA7915@tower.DHCP.thefacebook.com> Message-ID: <01000169702ee357-fe8b85e5-e601-41da-8ba2-25e8b7db52eb-000000@email.amazonses.com> References: <20190308041426.16654-1-tobin@kernel.org> <20190308041426.16654-3-tobin@kernel.org> <20190311215106.GA7915@tower.DHCP.thefacebook.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SES-Outgoing: 2019.03.12-54.240.9.46 Feedback-ID: 1.us-east-1.fQZZZ0Xtj2+TD7V5apTT/NrT6QKuPgzCT/IC7XYgDKI=:AmazonSES X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 11 Mar 2019, Roman Gushchin wrote: > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -4325,6 +4325,34 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags) > > return err; > > } > > > > +void kmem_cache_setup_mobility(struct kmem_cache *s, > > + kmem_cache_isolate_func isolate, > > + kmem_cache_migrate_func migrate) > > +{ > > I wonder if it's better to adapt kmem_cache_create() to take two additional > argument? I suspect mobility is not a dynamic option, so it can be > set on kmem_cache creation. One other idea that prior versions of this patchset used was to change kmem_cache_create() so that the ctor parameter becomes an ops vector. However, in order to reduce the size of the patchset I dropped that. It could be easily moved back to the way it was before. > > + /* > > + * Sadly serialization requirements currently mean that we have > > + * to disable fast cmpxchg based processing. > > + */ > > Can you, please, elaborate a bit more here? cmpxchg based processing does not lock the struct page. SMO requires to ensure that all changes on a slab page can be stopped. The page->lock will accomplish that. I think we could avoid dealing with actually locking the page with some more work.