linux-kernel - Re: Re: [PATCH v3 2/2] zram: try vmalloc() after kmalloc()

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Date:	Mon, 30 Nov 2015 19:42:02 +0900
From:	"kyeongdon.kim" <kyeongdon.kim@....com>
To:	Minchan Kim <minchan@...nel.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: Re: [PATCH v3 2/2] zram: try vmalloc() after kmalloc()

On 2015-11-30 오후 4:10, Minchan Kim wrote:
> On Fri, Nov 27, 2015 at 01:10:49PM +0900, Sergey Senozhatsky wrote:
>> From: Kyeongdon Kim <kyeongdon.kim@....com>
>>
>> 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 to allocate in that time, page allocation fails.
>> This patch makes to use vmalloc() as fallback of kmalloc(), this
>> prevents page alloc failure warning.
>>
>> After using this, we never found warning message in running test, also
>> It could reduce process startup latency about 60-120ms in each case.
>>
>> 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
>>
>> [minchan: change vmalloc gfp and adding comment about gfp]
>> [sergey: tweak comments and styles]
>> Signed-off-by: Kyeongdon Kim <kyeongdon.kim@....com>
>> Signed-off-by: Minchan Kim <minchan@...nel.org>
> 
> Kyeongdon, Could you test this patch on your device?
> 
> Thanks.

Sorry to have kept you waiting,
Obviously, I couldn't see allocation fail message with this patch.
But, there is something to make some delay(not sure yet this is normal).

static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
{
<snip>

   zstrm->private = comp->backend->create();
	            ^ // sometimes, return 'null' continually(2-5times)

As you know, if there is 'null' return, this function is called again to
get a memory in while() loop. I just checked this one with printk().

If you guys don't mind, I'll test more with trace log to check time delay.

However, If this is fully expectable status to you.
I think I don't need to do it.

Thanks,
Kyeongdon Kim
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