[lttng-dev] [PATCH lttng-modules] Fix: Building the event list fails on fragmented memory

[mathieu.desnoyers@efficios.com (Mathieu Desnoyers)]

Hi Martin,

Can you reformat your patch with diff -urN so I can apply it with patch ?

Thanks!

Mathieu

----- On Jun 8, 2015, at 11:19 AM, Martin Leisener martin at leisener.de wrote:

> Hi Mathieu,
> 
> thanks for merging my arm patch! I found one more issue during my lttng-modules
> usages,
> which can happen in low/fragmented memory situations. Please have a look, if you
> find this
> patch useful/mergable. Again it is tested on x86 Ubuntu 12.04 LTS as well as my
> imx6 arm board.
> 
> Regards Martin
> 
> 
> On a small arm imx6 solo with 256MB RAM it often happens that memory becomes
> fragmented rather
> quickly, so that kmalloc will not be able to get enough consecutive pages
> (enocuntered for
> example if you enable all kernel events: lttng enable-event -k syscall --all).
> 
> This patch switches the allocation to vmalloc. Tested for x86 on Ubuntu 12.04
> Lts
> and on imx6 solo 256MB RAM
> 
> If this patch is not applied, you can identify low and/or fragmented memory
> failures by
> looking at the kernel ring buffer (please ignore DMA, it is due to some memory
> setup
> misconfiguration, should read Normal):
> 
> ...
> [  321.993820] lttng-sessiond: page allocation failure: order:4, mode:0x1040d0
> ...
> [  321.994711] lowmem_reserve[]: 0 0 0
> [  321.994727] DMA: 801*4kB (UEMC) 424*8kB (EMC) 355*16kB (UEMC) 344*32kB (MC)
> 340*64kB (C) 8*128kB (C) 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB 0*8192kB
> 0*16384kB 0*32768kB = 46068kB
> 
> Signed-off-by: Martin Leisener <martin at leisener.de>
> ---
> lttng-events.c |   16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/lttng-events.c b/lttng-events.c
> index 7eec04c..c861f71 100644
> --- a/lttng-events.c
> +++ b/lttng-events.c
> @@ -39,6 +39,7 @@
> #include "wrapper/file.h"
> #include <linux/jhash.h>
> #include <linux/uaccess.h>
> +#include <linux/vmalloc.h>
>  #include "wrapper/uuid.h"
> #include "wrapper/vmalloc.h"	/* for wrapper_vmalloc_sync_all() */
> @@ -132,10 +133,10 @@ struct lttng_session *lttng_session_create(void)
> 			GFP_KERNEL);
> 	if (!metadata_cache)
> 		goto err_free_session;
> -	metadata_cache->data = kzalloc(METADATA_CACHE_DEFAULT_SIZE,
> -			GFP_KERNEL);
> +	metadata_cache->data = vmalloc(METADATA_CACHE_DEFAULT_SIZE);
> 	if (!metadata_cache->data)
> 		goto err_free_cache;
> +	memset(metadata_cache->data, 0, METADATA_CACHE_DEFAULT_SIZE);
> 	metadata_cache->cache_alloc = METADATA_CACHE_DEFAULT_SIZE;
> 	kref_init(&metadata_cache->refcount);
> 	session->metadata_cache = metadata_cache;
> @@ -162,7 +163,7 @@ void metadata_cache_destroy(struct kref *kref)
> {
> 	struct lttng_metadata_cache *cache =
> 		container_of(kref, struct lttng_metadata_cache, refcount);
> -	kfree(cache->data);
> +	vfree(cache->data);
> 	kfree(cache);
> }
> @@ -1523,10 +1524,15 @@ int lttng_metadata_printf(struct lttng_session *session,
> 		tmp_cache_alloc_size = max_t(unsigned int,
> 				session->metadata_cache->cache_alloc + len,
> 				session->metadata_cache->cache_alloc << 1);
> -		tmp_cache_realloc = krealloc(session->metadata_cache->data,
> -				tmp_cache_alloc_size, GFP_KERNEL);
> +		tmp_cache_realloc = vmalloc(tmp_cache_alloc_size);
> 		if (!tmp_cache_realloc)
> 			goto err;
> +		else if (session->metadata_cache->data) {
> +			memset(tmp_cache_realloc, 0, tmp_cache_alloc_size);
> +			memcpy(tmp_cache_realloc, session->metadata_cache->data,
> session->metadata_cache->cache_alloc);
> +			vfree(session->metadata_cache->data);
> +		}
> +
> 		session->metadata_cache->cache_alloc = tmp_cache_alloc_size;
> 		session->metadata_cache->data = tmp_cache_realloc;
> 	}
> --
> 1.7.9.5
> 
> 
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com