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Subject: Re: Number of arguments in vmalloc.c
References: <20181128140136.GG10377@bombadil.infradead.org>
From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <3264149f-e01e-faa2-3bc8-8aa1c255e075@suse.cz>
Date: Mon, 3 Dec 2018 14:59:36 +0100
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To: Matthew Wilcox <willy@infradead.org>, linux-mm@kvack.org

On 11/28/18 3:01 PM, Matthew Wilcox wrote:
> 
> Some of the functions in vmalloc.c have as many as nine arguments.
> So I thought I'd have a quick go at bundling the ones that make sense
> into a struct and pass around a pointer to that struct.  Well, it made
> the generated code worse,

Worse in which metric?

> so I thought I'd share my attempt so nobody
> else bothers (or soebody points out that I did something stupid).

I guess in some of the functions the args parameter could be const?
Might make some difference.

Anyway this shouldn't be a fast path, so even if the generated code is
e.g. somewhat larger, then it still might make sense to reduce the
insane parameter lists.

> I tried a few variations on this theme; bundling gfp_t and node into
> the struct made it even worse, as did adding caller and vm_flags.  This
> is the least bad version.
> 
> (Yes, the naming is bad; I'm not tidying this up for submission, I'm
> showing an experiment that didn't work).
> 
> Nacked-by: Matthew Wilcox <willy@infradead.org>
>