RE: [PATCH v2 1/2] fork: add clone3

[David Laight <David.Laight@ACULAB.COM>]

From: Christian Brauner
> Sent: 04 June 2019 10:43
...
> > > +	u64 clone_flags = args->flags;
> > > +	int __user *child_tidptr = args->child_tid;
> > > +	unsigned long tls = args->tls;
> > > +	unsigned long stack_start = args->stack;
> > > +	unsigned long stack_size = args->stack_size;
> >
> > Some of these are only used once, so it's probably not worth sticking them in
> > local variables.
> 
> [1]:
> Ok, will double check.
> This was just to minimize copy-paste erros for variables which were used
> multiple times.

Even the ones that are used multiple times may be better being
repeatedly read from args->xxx.

If you are "lucky" 'args' will be in a register variables
so all the accesses are cheap.
With too many locals everything gets copied onto the actual
stack - especially likely if there are any function calls
(that might conceivably change *args) after the locals
are initialised.

	David

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