From: Nick Piggin <[email protected]>
Date: Fri, 18 May 2007 06:08:54 +0200
> I'd like to be the first to propose an increase to the size of struct page
> just for the sake of increasing it!
>
> If we add 8 bytes to struct page on 64-bit machines, it becomes 64 bytes,
> which is quite a nice number for cache purposes.
>
> However we don't have to let those 8 bytes go to waste: we can use them
> to store the virtual address of the page, which kind of makes sense for
> 64-bit, because they can likely to use complicated memory models.
>
> I'd say all up this is going to decrease overall cache footprint in
> fastpaths, both by reducing text and data footprint of page_address and
> related operations, and by reducing cacheline footprint of most batched
> operations on struct pages.
>
> Flame away :)
I've toyed with this several times on sparc64, and in my experience
the extra memory reference on page->virtual costs on average about the
same as the non-power-of-2 pointer arithmetic.
The decision is absolutely arbitrary performance wise, but if you
consider the memory wastage on enormous systems going without
page->virtual I think is clearly better.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
