Re: [PATCH v2] zram: Prevent page allocation failure during zcomp_strm_alloc

[Minchan Kim <minchan@kernel.org>]

Hello,

On Fri, Nov 20, 2015 at 07:02:44PM +0900, Kyeongdon Kim wrote:
> When we're using LZ4 multi compression streams for zram swap,
> we found out page allocation failure message in system running test.
> That was not only once, but a few(2 - 5 times per test).
> Also, some failure cases were continually occurring to try allocation
> order 3.
> 
> In order to make parallel compression private data, we should call
> kzalloc() with order 2/3 in runtime(lzo/lz4). But if there is no order
>  2/3 size memory in that time, page allocation fails.
> This patch makes to use vmalloc() as fallback of kmalloc(), this
> prevents page alloc failure warning.
> 
> After this, we never found warning message in running test, also
> It could reduce process startup latency about 60-120ms in each case.

Very nice!

> 
> For reference a call trace :
> 
> Binder_1: page allocation failure: order:3, mode:0x10c0d0
> CPU: 0 PID: 424 Comm: Binder_1 Tainted: GW 3.10.49-perf-g991d02b-dirty #20
> Call trace:
> [<ffffffc0002069c8>] dump_backtrace+0x0/0x270
> [<ffffffc000206c48>] show_stack+0x10/0x1c
> [<ffffffc000cb51c8>] dump_stack+0x1c/0x28
> [<ffffffc0002bbfc8>] warn_alloc_failed+0xfc/0x11c
> [<ffffffc0002bf518>] __alloc_pages_nodemask+0x724/0x7f0
> [<ffffffc0002bf5f8>] __get_free_pages+0x14/0x5c
> [<ffffffc0002ed6a4>] kmalloc_order_trace+0x38/0xd8
> [<ffffffc0005d9738>] zcomp_lz4_create+0x2c/0x38
> [<ffffffc0005d78f0>] zcomp_strm_alloc+0x34/0x78
> [<ffffffc0005d7a58>] zcomp_strm_multi_find+0x124/0x1ec
> [<ffffffc0005d7c14>] zcomp_strm_find+0xc/0x18
> [<ffffffc0005d8fa0>] zram_bvec_rw+0x2fc/0x780
> [<ffffffc0005d9680>] zram_make_request+0x25c/0x2d4
> [<ffffffc00040f8ac>] generic_make_request+0x80/0xbc
> [<ffffffc00040f98c>] submit_bio+0xa4/0x15c
> [<ffffffc0002e8bb0>] __swap_writepage+0x218/0x230
> [<ffffffc0002e8c04>] swap_writepage+0x3c/0x4c
> [<ffffffc0002c7384>] shrink_page_list+0x51c/0x8d0
> [<ffffffc0002c7e88>] shrink_inactive_list+0x3f8/0x60c
> [<ffffffc0002c86c8>] shrink_lruvec+0x33c/0x4cc
> [<ffffffc0002c8894>] shrink_zone+0x3c/0x100
> [<ffffffc0002c8c10>] try_to_free_pages+0x2b8/0x54c
> [<ffffffc0002bf308>] __alloc_pages_nodemask+0x514/0x7f0
> [<ffffffc0002bf5f8>] __get_free_pages+0x14/0x5c
> [<ffffffc0003446cc>] proc_info_read+0x50/0xe4
> [<ffffffc0002f5204>] vfs_read+0xa0/0x12c
> [<ffffffc0002f59c8>] SyS_read+0x44/0x74
> DMA: 3397*4kB (MC) 26*8kB (RC) 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB
>      0*512kB 0*1024kB 0*2048kB 0*4096kB = 13796kB
> 
> Signed-off-by: Kyeongdon Kim <kyeongdon.kim@lge.com>

If you fix kvfree Sergey pointed out, you can add my

        Acked-by: Minchan Kim <minchan@kernel.org>

> ---
>  drivers/block/zram/zcomp_lz4.c | 15 +++++++++++++--
>  drivers/block/zram/zcomp_lzo.c | 15 +++++++++++++--
>  2 files changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/zram/zcomp_lz4.c b/drivers/block/zram/zcomp_lz4.c
> index f2afb7e..0477894 100644
> --- a/drivers/block/zram/zcomp_lz4.c
> +++ b/drivers/block/zram/zcomp_lz4.c
> @@ -10,17 +10,28 @@
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/lz4.h>
> +#include <linux/vmalloc.h>
> +#include <linux/mm.h>
>  
>  #include "zcomp_lz4.h"
>  
>  static void *zcomp_lz4_create(void)
>  {
> -	return kzalloc(LZ4_MEM_COMPRESS, GFP_KERNEL);
> +	void *ret;
> +
> +	ret = kzalloc(LZ4_MEM_COMPRESS,
> +			__GFP_NORETRY|__GFP_NOWARN|__GFP_NOMEMALLOC);
> +	if (!ret)
> +		ret = vzalloc(LZ4_MEM_COMPRESS);

One thing I feel bad smell is that call vzalloc with GFP_KERNEL.
This function can be called in direct reclaim path with holding
fs lock and GFP_KERNEL can enter recursive reclaim path so
lockdep would complain theoretically if I don't miss something.

If it is true, we should fix several allocation flags in
zcomp_strm_alloc. I just want to record this warning for the future
in this thread so someone who is finding for the contribution
material will prove and fix it. :)


> +	return ret;
>  }
>  
>  static void zcomp_lz4_destroy(void *private)
>  {
> -	kfree(private);
> +	if (is_vmalloc_addr(private))
> +		vfree(private);
> +	else
> +		kfree(private);

>  }
>  
>  static int zcomp_lz4_compress(const unsigned char *src, unsigned char *dst,
> diff --git a/drivers/block/zram/zcomp_lzo.c b/drivers/block/zram/zcomp_lzo.c
> index da1bc47..613fbac 100644
> --- a/drivers/block/zram/zcomp_lzo.c
> +++ b/drivers/block/zram/zcomp_lzo.c
> @@ -10,17 +10,28 @@
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/lzo.h>
> +#include <linux/vmalloc.h>
> +#include <linux/mm.h>
>  
>  #include "zcomp_lzo.h"
>  
>  static void *lzo_create(void)
>  {
> -	return kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> +	void *ret;
> +
> +	ret = kzalloc(LZO1X_MEM_COMPRESS,
> +			__GFP_NORETRY|__GFP_NOWARN|__GFP_NOMEMALLOC);
> +	if (!ret)
> +		ret = vzalloc(LZO1X_MEM_COMPRESS);
> +	return ret;
>  }
>  
>  static void lzo_destroy(void *private)
>  {
> -	kfree(private);
> +	if (is_vmalloc_addr(private))
> +		vfree(private);
> +	else
> +		kfree(private);
>  }
>  
>  static int lzo_compress(const unsigned char *src, unsigned char *dst,
> -- 
> 1.8.2
>