The patch titled
tcp.c: calculate tcp_mem based on low memory instead of all memory
has been added to the -mm tree. Its filename is
tcpc-calculate-tcp_mem-based-on-low-memory-instead-of-all-memory.patch
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Subject: tcp.c: calculate tcp_mem based on low memory instead of all memory
From: Miquel van Smoorenburg <miquels@xxxxxxxxxx>
I started upgrading a bunch of machines in my nntp server farm
to a recent kernel- 2.6.25.x. They were running 2.6.11.12 on
32 bits, and I upgraded them to 2.6.25.x on 64 bits.
All went fine until I noticed a few machines didn't have a 64
bit capable processor, so I had to keep them on a 32 bit kernel.
These are machines with dual xeons 3 Ghz and 8 GB of RAM.
On the 32 bit machines I keep getting the error below, and a flood
of these on a 9600 baud serial console essentially kills the machine:
diablo invoked oom-killer: gfp_mask=0xd0, order=0, oomkilladj=0
Pid: 4459, comm: diablo Not tainted 2.6.25.7-rc1 #1
[<c0249660>] oom_kill_process+0x120/0x210
[<c0227ff8>] __capable+0x8/0x20
[<c0249898>] badness+0x128/0x1c0
[<c0249b1c>] out_of_memory+0x17c/0x1c0
[<c024bdf4>] __alloc_pages+0x254/0x350
[<c03b75ad>] tcp_sendmsg+0x5cd/0xb50
[<c0381672>] sock_aio_write+0xe2/0x100
[<c02681e7>] do_sync_write+0xc7/0x110
[<c0232f20>] autoremove_wake_function+0x0/0x50
[<c0268af3>] vfs_write+0x133/0x140
[<c0269131>] sys_write+0x41/0x70
[<c0202e5e>] syscall_call+0x7/0xb
After some investigation, I found out that the values of
/proc/sys/net/ipv4/tcp_mem are quite different between
these two versions:
2.6.11.12:
$ cat tcp_mem
98304 131072 196608
2.6.25:
# cat tcp_mem
804672 1072896 1609344
Somwehere between 2.6.11.12 and 2.6.25, the calculation method of
the tcp_mem array was changed. Now 1609344 pages is 6.5 GB,
and that will ofcourse never fit in x86_32's low memory ..
I am not quite sure what the correct solution is here, I think
something like the patch below.
Alternatively we could use the existing calculation but limit 'limit'
to 3/4 of (totalram_pages - totalhigh_pages) if (totalhigh_pages > 0) ?
linux-2.6.26-tcp_mem-lowmem.patch
[PATCH] tcp.c: calculate tcp_mem based on low memory instead of all memory
The tcp_mem array which contains limits on the total amount of
memory used by TCP sockets is calculated based on nr_all_pages.
On a 32 bits x86 system, we should base this on the number of
lowmem pages.
Signed-off-by: Miquel van Smoorenburg <miquels@xxxxxxxxxx>
Cc: John Heffner <jheffner@xxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
net/ipv4/tcp.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff -puN net/ipv4/tcp.c~tcpc-calculate-tcp_mem-based-on-low-memory-instead-of-all-memory net/ipv4/tcp.c
--- a/net/ipv4/tcp.c~tcpc-calculate-tcp_mem-based-on-low-memory-instead-of-all-memory
+++ a/net/ipv4/tcp.c
@@ -260,6 +260,8 @@
#include <linux/socket.h>
#include <linux/random.h>
#include <linux/bootmem.h>
+#include <linux/highmem.h>
+#include <linux/swap.h>
#include <linux/cache.h>
#include <linux/err.h>
#include <linux/crypto.h>
@@ -2620,7 +2622,7 @@ __setup("thash_entries=", set_thash_entr
void __init tcp_init(void)
{
struct sk_buff *skb = NULL;
- unsigned long limit;
+ unsigned long nr_pages, limit;
int order, i, max_share;
BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > sizeof(skb->cb));
@@ -2689,8 +2691,9 @@ void __init tcp_init(void)
* is up to 1/2 at 256 MB, decreasing toward zero with the amount of
* memory, with a floor of 128 pages.
*/
- limit = min(nr_all_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
- limit = (limit * (nr_all_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
+ nr_pages = totalram_pages - totalhigh_pages;
+ limit = min(nr_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
+ limit = (limit * (nr_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
limit = max(limit, 128UL);
sysctl_tcp_mem[0] = limit / 4 * 3;
sysctl_tcp_mem[1] = limit;
_
Patches currently in -mm which might be from miquels@xxxxxxxxxx are
tcpc-calculate-tcp_mem-based-on-low-memory-instead-of-all-memory.patch
scsi-dpt_i2o-is-bust-on-ia64.patch
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