Messages in this thread | | | Date | Tue, 1 Dec 2015 13:44:45 +0900 | From | Minchan Kim <> | Subject | Re: Re: Re: [PATCH v3 2/2] zram: try vmalloc() after kmalloc() |
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On Tue, Dec 01, 2015 at 11:31:41AM +0900, kyeongdon.kim wrote: > On 2015-12-01 오전 8:18, Minchan Kim wrote: > > Hi Kyeongdon, > > > > On Mon, Nov 30, 2015 at 07:42:02PM +0900, kyeongdon.kim wrote: > > > >> > On Fri, Nov 27, 2015 at 01:10:49PM +0900, Sergey Senozhatsky wrote: > >> >> From: Kyeongdon Kim <kyeongdon.kim@lge.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@lge.com> > >> >> Signed-off-by: Minchan Kim <minchan@kernel.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). > > > > You mean new changes makes start-up delay of your application sometime > > still, > > but not frequent like old? > > > I couldn't see start-up delay during my test after this patch. > But, I checked the return value from alloc function like the below : > > static void *zcomp_lz4_create(void) > <snip> > ret = kzalloc(LZ4_MEM_COMPRESS, GFP_NOIO | __GFP_NORETRY | > __GFP_NOWARN | __GFP_NOMEMALLOC); > printk("%s: %d: ret = %p\n",__func__,__LINE__,ret); //line 32 > if (!ret) { > ret = __vmalloc(LZ4_MEM_COMPRESS, > GFP_NOIO | __GFP_NORETRY | __GFP_NOWARN | > __GFP_NOMEMALLOC | __GFP_ZERO | __GFP_HIGHMEM, > PAGE_KERNEL); > printk("%s: %d: ret = %p\n",__func__,__LINE__,ret); //line 38 > } > return ret;
OK, I got it.
> > log message : > [ 352.226014][0] zcomp_lz4_create: 32: ret = (null) > [ 352.226035][0] zcomp_lz4_create: 38: ret = (null) > [ 352.226791][0] zcomp_lz4_create: 32: ret = (null) > [ 352.226809][0] zcomp_lz4_create: 38: ret = (null) > [ 352.230348][0] zcomp_lz4_create: 32: ret = (null) > [ 352.230369][0] zcomp_lz4_create: 38: ret = (null) > [ 352.230460][0] zcomp_lz4_create: 32: ret = (null) > [ 352.230485][0] zcomp_lz4_create: 38: ret = (null) > [ 352.230507][0] zcomp_lz4_create: 32: ret = (null) > [ 352.230520][0] zcomp_lz4_create: 38: ret = (null) > [ 352.230608][0] zcomp_lz4_create: 32: ret = (null) > [ 352.230619][0] zcomp_lz4_create: 38: ret = (null) > [ 352.230888][0] zcomp_lz4_create: 32: ret = (null) > [ 352.230902][0] zcomp_lz4_create: 38: ret = (null) > [ 352.231406][0] zcomp_lz4_create: 32: ret = ffffffc002088000 > [ 352.234024][0] zcomp_lz4_create: 32: ret = (null) > [ 352.234060][0] zcomp_lz4_create: 38: ret = (null) > [ 352.234359][0] zcomp_lz4_create: 32: ret = (null) > [ 352.234384][0] zcomp_lz4_create: 38: ret = (null) > [ 352.234618][0] zcomp_lz4_create: 32: ret = (null) > [ 352.234639][0] zcomp_lz4_create: 38: ret = (null) > [ 352.234667][0] zcomp_lz4_create: 32: ret = (null) > [ 352.234685][0] zcomp_lz4_create: 38: ret = (null) > [ 352.234738][0] zcomp_lz4_create: 32: ret = (null) > [ 352.234748][0] zcomp_lz4_create: 38: ret = (null) > [ 352.234800][0] zcomp_lz4_create: 32: ret = (null) > [ 352.234816][0] zcomp_lz4_create: 38: ret = (null) > [ 352.234852][0] zcomp_lz4_create: 32: ret = (null) > [ 352.234865][0] zcomp_lz4_create: 38: ret = (null) > [ 352.235136][0] zcomp_lz4_create: 32: ret = (null) > [ 352.235179][0] zcomp_lz4_create: 38: ret = ffffff80016a4000 > > I thought this pattern from vmalloc is not normal. > >> > >> static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp) > >> { > >> <snip> > >> > >> zstrm->private = comp->backend->create(); > >> ^ // sometimes, return 'null' continually(2-5times) > > > > Hmm, I think it is caused by __GFP_NOMEMALLOC. > > Could you test it without the flag? > > > >> > >> 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. > > > > No problem. > > > >> > >> However, If this is fully expectable status to you. > >> I think I don't need to do it. > > > > It's not what I expected. Actually, I thought failure of vmalloc > > in that place should be *really really* rare. I think it's caused by > > __GFP_NOMEMALLOC so I want to see test result without the flag. > > > > Thanks for the careful test! > > > You're welcome. > > After I removed flag '__GFP_NOMEMALLOC', I couldn't find return 'null' > from vmalloc until now.
Thanks for the test. You said you cannot see the delay any more so it's fine as it is.
Regardless of it, I want to remove __GFP_NOMEMALLOC in the gfp_mask. The reason we decided to add vmalloc fallback is that we expect that it is likely to succeed a few order-0 pages to allocate (sizeof(buffer) > PAGE_SIZE) although it was failed by kmalloc. But what I missing is that zram-swap is working in direct reclaim normally so it is more flexible to use emegency memory pool( e,g, zsmalloc doesn't use __GFP_NOMEMALLOC) so there is no point to use __GFP_NOMEMALLOC in here.
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