From: Andrew Morton <akpm@osdl.org>
To: jbarnes@sgi.com (Jesse Barnes)
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] use NODES_SHIFT to calculate ZONE_SHIFT
Date: Fri, 7 Nov 2003 13:58:06 -0800 [thread overview]
Message-ID: <20031107135806.3c929688.akpm@osdl.org> (raw)
In-Reply-To: <20031105211608.GA23560@sgi.com>
jbarnes@sgi.com (Jesse Barnes) wrote:
>
> Now that we have a proper NODES_SHIFT value, we need to use it to define
> ZONE_SHIFT otherwise we'll spill over 8 bits if we have more than 85
> nodes. How does this look? The '+2' should really be
> log2(MAX_NR_NODES), but I think this is an improvement over what was
> there.
You mean log2(MAX_NR_ZONES).
How about we do it this way, so at least the duplicated information is on
adjacent lines, and they are unlikely to get out of sync?
diff -puN include/linux/mm.h~ZONE_SHIFT-from-NODES_SHIFT include/linux/mm.h
--- 25/include/linux/mm.h~ZONE_SHIFT-from-NODES_SHIFT Fri Nov 7 13:51:22 2003
+++ 25-akpm/include/linux/mm.h Fri Nov 7 13:55:11 2003
@@ -322,8 +322,10 @@ static inline void put_page(struct page
/*
* The zone field is never updated after free_area_init_core()
* sets it, so none of the operations on it need to be atomic.
+ * We'll have up to log2(MAX_NUMNODES * MAX_NR_ZONES) zones
+ * total, so we use NODES_SHIFT here to get enough bits.
*/
-#define ZONE_SHIFT (BITS_PER_LONG - 8)
+#define ZONE_SHIFT (BITS_PER_LONG - NODES_SHIFT - MAX_NR_ZONES_SHIFT)
struct zone;
extern struct zone *zone_table[];
diff -puN include/linux/mmzone.h~ZONE_SHIFT-from-NODES_SHIFT include/linux/mmzone.h
--- 25/include/linux/mmzone.h~ZONE_SHIFT-from-NODES_SHIFT Fri Nov 7 13:51:49 2003
+++ 25-akpm/include/linux/mmzone.h Fri Nov 7 13:57:19 2003
@@ -159,7 +159,10 @@ struct zone {
#define ZONE_DMA 0
#define ZONE_NORMAL 1
#define ZONE_HIGHMEM 2
-#define MAX_NR_ZONES 3
+
+#define MAX_NR_ZONES 3 /* Sync this with MAX_NR_ZONES_SHIFT */
+#define MAX_NR_ZONES_SHIFT 2 /* ceil(log2(MAX_NR_ZONES)) */
+
#define GFP_ZONEMASK 0x03
/*
_
next prev parent reply other threads:[~2003-11-07 22:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-05 21:16 [PATCH] use NODES_SHIFT to calculate ZONE_SHIFT Jesse Barnes
2003-11-07 21:58 ` Andrew Morton [this message]
2003-11-07 22:01 ` Jesse Barnes
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20031107135806.3c929688.akpm@osdl.org \
--to=akpm@osdl.org \
--cc=jbarnes@sgi.com \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).