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Date:   Mon, 28 Feb 2022 14:30:11 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Marco Elver <elver@google.com>
Cc:     Kees Cook <keescook@chromium.org>, llvm@lists.linux.dev,
        Pekka Enberg <penberg@kernel.org>,
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        Nick Desaulniers <ndesaulniers@google.com>,
        Daniel Micay <danielmicay@gmail.com>,
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Subject: Re: [PATCH] mm: Handle ksize() vs __alloc_size by forgetting size
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On Mon, Feb 28, 2022 at 12:24:51PM +0100, Marco Elver wrote:
> 2. Somehow statically computing the size-class's size (kmalloc_index()
> might help here), removing __alloc_size from allocation functions and
> instead use some wrapper.

I don't think that's computable.  I have been thinking about a slab flag
that would say "speed is more important than size; if the smallest slab
for this size of allocation has no free objects, search larger slabs
to get memory instead of allocating a new slab".  If we did have such
a feature, it would be impossible to know how large ksize() would report.