RE: [patch] add an iterator index in struct pagevec
Andrew Morton wrote on Monday, December 04, 2006 9:45 PM > On Mon, 4 Dec 2006 21:21:31 -0800 > "Chen, Kenneth W" <[EMAIL PROTECTED]> wrote: > > > pagevec is never expected to be more than PAGEVEC_SIZE, I think a > > unsigned char is enough to count them. This patch makes nr, cold > > to be unsigned char > > Is that on the right side of the speed/space tradeoff? I haven't measured speed. Size wise, making them char shrinks vmlinux text size by 112 bytes on x86_64 (using default config option). > I must say I'm a bit skeptical about the need for this. But I haven't > looked closely at the blockdev-specific dio code yet. It was suggested to declare another struct that embeds pagevec to perform iteration. But I prefer to have pagevec having the capability, it is more compact this way. It would be nice if you can review blockdev-specific dio code. I would appreciate it very much. - Ken - 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/
Re: [patch] add an iterator index in struct pagevec
On Mon, 4 Dec 2006 21:21:31 -0800
"Chen, Kenneth W" <[EMAIL PROTECTED]> wrote:
> pagevec is never expected to be more than PAGEVEC_SIZE, I think a
> unsigned char is enough to count them. This patch makes nr, cold
> to be unsigned char
Is that on the right side of the speed/space tradeoff?
> and also adds an iterator index. With that,
> the size can be even bumped up by 1 to 15.
>
> Signed-off-by: Ken Chen <[EMAIL PROTECTED]>
>
>
> diff -Nurp linux-2.6.19/include/linux/pagevec.h
> linux-2.6.19.ken/include/linux/pagevec.h
> --- linux-2.6.19/include/linux/pagevec.h 2006-11-29 13:57:37.0
> -0800
> +++ linux-2.6.19.ken/include/linux/pagevec.h 2006-12-04 19:18:21.0
> -0800
> @@ -8,15 +8,16 @@
> #ifndef _LINUX_PAGEVEC_H
> #define _LINUX_PAGEVEC_H
>
> -/* 14 pointers + two long's align the pagevec structure to a power of two */
> -#define PAGEVEC_SIZE 14
> +/* 15 pointers + 3 char's align the pagevec structure to a power of two */
> +#define PAGEVEC_SIZE 15
>
> struct page;
> struct address_space;
>
> struct pagevec {
> - unsigned long nr;
> - unsigned long cold;
> + unsigned char nr;
> + unsigned char cold;
> + unsigned char idx;
> struct page *pages[PAGEVEC_SIZE];
> };
>
I'd have thought that pagevec_init() would want to be involved in this, no?
I must say I'm a bit skeptical about the need for this. But I haven't
looked closely at the blockdev-specific dio code yet.
-
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Re: [patch] add an iterator index in struct pagevec
On Mon, 4 Dec 2006 21:21:31 -0800
Chen, Kenneth W [EMAIL PROTECTED] wrote:
pagevec is never expected to be more than PAGEVEC_SIZE, I think a
unsigned char is enough to count them. This patch makes nr, cold
to be unsigned char
Is that on the right side of the speed/space tradeoff?
and also adds an iterator index. With that,
the size can be even bumped up by 1 to 15.
Signed-off-by: Ken Chen [EMAIL PROTECTED]
diff -Nurp linux-2.6.19/include/linux/pagevec.h
linux-2.6.19.ken/include/linux/pagevec.h
--- linux-2.6.19/include/linux/pagevec.h 2006-11-29 13:57:37.0
-0800
+++ linux-2.6.19.ken/include/linux/pagevec.h 2006-12-04 19:18:21.0
-0800
@@ -8,15 +8,16 @@
#ifndef _LINUX_PAGEVEC_H
#define _LINUX_PAGEVEC_H
-/* 14 pointers + two long's align the pagevec structure to a power of two */
-#define PAGEVEC_SIZE 14
+/* 15 pointers + 3 char's align the pagevec structure to a power of two */
+#define PAGEVEC_SIZE 15
struct page;
struct address_space;
struct pagevec {
- unsigned long nr;
- unsigned long cold;
+ unsigned char nr;
+ unsigned char cold;
+ unsigned char idx;
struct page *pages[PAGEVEC_SIZE];
};
I'd have thought that pagevec_init() would want to be involved in this, no?
I must say I'm a bit skeptical about the need for this. But I haven't
looked closely at the blockdev-specific dio code yet.
-
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/
RE: [patch] add an iterator index in struct pagevec
Andrew Morton wrote on Monday, December 04, 2006 9:45 PM On Mon, 4 Dec 2006 21:21:31 -0800 Chen, Kenneth W [EMAIL PROTECTED] wrote: pagevec is never expected to be more than PAGEVEC_SIZE, I think a unsigned char is enough to count them. This patch makes nr, cold to be unsigned char Is that on the right side of the speed/space tradeoff? I haven't measured speed. Size wise, making them char shrinks vmlinux text size by 112 bytes on x86_64 (using default config option). I must say I'm a bit skeptical about the need for this. But I haven't looked closely at the blockdev-specific dio code yet. It was suggested to declare another struct that embeds pagevec to perform iteration. But I prefer to have pagevec having the capability, it is more compact this way. It would be nice if you can review blockdev-specific dio code. I would appreciate it very much. - Ken - 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/
