Re: 2.6.10-rc1-mm4 -1 EAGAIN after allocation failure was: Re: Kernel 2.6.9 Multiple Page Allocation Failures

Nick Piggin
2004-11-10T04:27:05Z

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Stefan Schmidt wrote:

>On Tue, Nov 09, 2004 at 05:39:20PM -0800, Andrew Morton wrote:
>
>>Well you've definitely used up all the memory which is available for atomic
>>allocations. Are you using an increased /proc/sys/vm/min_free_kbytes there?
>>
>Yes, vm.min_free_kbytes=8192.
>For other vm-settings find sysctl.conf attached.
>
>Netdev: tg3 BCM5704r03, TSO off, ~32kpps rx, ~35kpps tx, ~2 rx errors/s
>
>
>>As for the application collapse: dunno. Maybe networking broke. It would
>>be interesting to test Linus's current tree, at
>>ftp://ftp.kernel.org/pub/linux/kernel/v2.6/snapshots/patch-2.6.10-rc1-bk19.gz
>>
>Will try that tomorrow. Would you suggest printing out show_free_areas();
>there too? I don't know what kind of an overhead that will generate on
>subsequent stack traces.
>
>

Stefan,
Can you try the following patch, please? It is diffed against 2.6.10-rc1,
but I think it should apply to -mm kernels as well.

Basically 2.6.8 and earlier kernels had some quirks in the page allocator
that would allow for example, a large portion of "DMA" memory to be reserved
for network memory allocations (atomic allocations). After 'fixing' this
problem, 2.6.9 is effectively left with about a quarter the amount of memory
reserved for network allocations compared with 2.6.8.

The following patch roughly restores parity there. Thanks.

Nick

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---

linux-2.6-npiggin/mm/page_alloc.c | 41 +++++++++++++++++++++-----------------
1 files changed, 23 insertions(+), 18 deletions(-)

diff -puN mm/page_alloc.c~mm-restore-atomic-buffer mm/page_alloc.c
--- linux-2.6/mm/page_alloc.c~mm-restore-atomic-buffer 2004-11-10 15:13:33.000000000 +1100
+++ linux-2.6-npiggin/mm/page_alloc.c 2004-11-10 14:57:54.000000000 +1100
@@ -1935,8 +1935,12 @@ static void setup_per_zone_pages_min(voi
lowmem_pages;
}

- zone->pages_low = zone->pages_min * 2;
- zone->pages_high = zone->pages_min * 3;
+ /*
+ * When interpreting these watermarks, just keep in mind that:
+ * zone->pages_min == (zone->pages_min * 4) / 4;
+ */
+ zone->pages_low = (zone->pages_min * 5) / 4;
+ zone->pages_high = (zone->pages_min * 6) / 4;
spin_unlock_irqrestore(&zone->lru_lock, flags);
}
}
@@ -1945,24 +1949,25 @@ static void setup_per_zone_pages_min(voi
* Initialise min_free_kbytes.
*
* For small machines we want it small (128k min). For large machines
- * we want it large (16MB max). But it is not linear, because network
+ * we want it large (64MB max). But it is not linear, because network
* bandwidth does not increase linearly with machine size. We use
*
- * min_free_kbytes = sqrt(lowmem_kbytes)
+ * min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
+ * min_free_kbytes = sqrt(lowmem_kbytes * 16)
*
* which yields
*
- * 16MB: 128k
- * 32MB: 181k
- * 64MB: 256k
- * 128MB: 362k
- * 256MB: 512k
- * 512MB: 724k
- * 1024MB: 1024k
- * 2048MB: 1448k
- * 4096MB: 2048k
- * 8192MB: 2896k
- * 16384MB: 4096k
+ * 16MB: 512k
+ * 32MB: 724k
+ * 64MB: 1024k
+ * 128MB: 1448k
+ * 256MB: 2048k
+ * 512MB: 2896k
+ * 1024MB: 4096k
+ * 2048MB: 5792k
+ * 4096MB: 8192k
+ * 8192MB: 11584k
+ * 16384MB: 16384k
*/
static int __init init_per_zone_pages_min(void)
{
@@ -1970,11 +1975,11 @@ static int __init init_per_zone_pages_mi

lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10);

- min_free_kbytes = int_sqrt(lowmem_kbytes);
+ min_free_kbytes = int_sqrt(lowmem_kbytes * 16);
if (min_free_kbytes < 128)
min_free_kbytes = 128;
- if (min_free_kbytes > 16384)
- min_free_kbytes = 16384;
+ if (min_free_kbytes > 65536)
+ min_free_kbytes = 65536;
setup_per_zone_pages_min();
setup_per_zone_protection();
return 0;

_