linux-kernel - Re: [PATCH tip/core/rcu 1/2] rcu: Support kfree_bulk() interface in kfree

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Date:   Mon, 24 Feb 2020 17:11:36 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     paulmck@...nel.org, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>
Subject: Re: [PATCH tip/core/rcu 1/2] rcu: Support kfree_bulk() interface in
 kfree_rcu()

> >  
> > +/*
> > + * This macro defines how many entries the "records" array
> > + * will contain. It is based on the fact that the size of
> > + * kfree_rcu_bulk_data structure becomes exactly one page.
> > + */
> > +#define KFREE_BULK_MAX_ENTR ((PAGE_SIZE / sizeof(void *)) - 3)
> > +
> 
> Why use the "magic" number "3" here? Could we just define struct
> kfree_rcu_bulk_data as:
> 
> struct kfree_rcu_bulk_data {
> 	struct kfree_rcu_bulk_data *next;
> 	struct rcu_head *head_free_debug;
> 	unsigned long nr_records;
> 	void *records[];
> }
> 
> ?
> 
> And the the above macro becomes:
> 
> #define KFREE_BULK_MAX_ENTR ((PAGE_SIZE - sizeof(struct kfree_rcu_bulk_data)) / sizeof(void *))
> 
That should work. I agree that looks better :)

We can fix that by submitting a separate patch.

Thank you!

--
Vlad Rezki