On Thu, Nov 20, 2014 at 8:05 PM, <zhiyuan_zhu@xxxxxxx> wrote:
Hi Greg/Michal
Very sorry I have a mistake in previous mail. (It should be nr_file_pages not nr_free_pages)
I rearrange this problem.
// *********** log begin **********
6 161030.084144 2014-11-07 21:44:53.304 lowmemorykiller: Killing 'om.htc.launcher' (4486), adj 294,
6 161030.084144 2014-11-07 21:44:53.304 to free 47856kB on behalf of 'kworker/u8:14' (20594) because
6 161030.084144 2014-11-07 21:44:53.304 cache 72460kB is below limit 73728kB for oom_score_adj 235
// **** /proc/meminfo 's result
4 161030.084797 2014-11-07 21:44:53.304 Cached: 142448 kB
// *********** log end **********
After I checked the android's low memory strategy: kernel/drivers/staging/android/lowmemorykiller.c
// ****** code begin *********
other_file = global_page_state(NR_FILE_PAGES) -
global_page_state(NR_SHMEM) -
total_swapcache_pages();
lowmem_print(1, "Killing '%s' (%d), adj %hd,\n" \
" to free %ldkB on behalf of '%s' (%d) because\n" \
" cache %ldkB is below limit %ldkB for oom_score_adj %hd\n" \
" Free memory is %ldkB above reserved\n",
selected->comm, selected->pid,
selected_oom_score_adj,
selected_tasksize * (long)(PAGE_SIZE / 1024),
current->comm, current->pid,
other_file * (long)(PAGE_SIZE / 1024),
minfree * (long)(PAGE_SIZE / 1024),
min_score_adj,
other_free * (long)(PAGE_SIZE / 1024));
// ******* code end ************
So android's strategy's free memory is = other_file = (nr file pages - nr shmem - total swapcache pages) * 4K = [cache 72460kB]
But the system's free memory is: Cached: 142448 kB // from /proc/meminfo
And system's free memory is: Cached + MemFree + Buffers is largely than the memory which anroid lowmemorykiller calculated memory [cache 72460K]
At this time point, system will kill some important processes, but system have enough memory.
This is android's lowmemorykiller defect? or Linux kernel memory's defect?
So I have some questions:
I have a question: what's the nr file pages mean? What different between nr_file_pages from Cached (from /proc/meminfo)?
And nr shmem, swapcache pages are small, so I think this is the key problem why android's stragegy calculated free memory is largely less than /proc/meminfo Cached's value.Why lowmemkiller -total_swapcache_pages()? see commit 058dbde92:
staging: android: lowmemorykiller: neglect swap cached pages in other_file
With ZRAM enabled it is observed that lowmemory killer
doesn't trigger properly. swap cached pages are
accounted in NR_FILE, and lowmemorykiller considers
this as reclaimable and adds to other_file. But these
pages can't be reclaimed unless lowmemorykiller triggers.
So subtract swap pages from other_file.
and commit 31d59a4198f will also make help, please check it.
Thanks Zhiyuan zhu -----邮件原件----- 发件人: Michal Hocko [mailto:mhocko@xxxxxxx] 发送时间: 2014年11月20日 18:19 收件人: Zhiyuan Zhu(朱志遠) 抄送: hannes@xxxxxxxxxxx; Future Zhou(周未來); Rachel Zhang(張瑩); bsingharora@xxxxxxxxx; kamezawa.hiroyu@xxxxxxxxxxxxxx; cgroups@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; greg@xxxxxxxxx 主题: Re: 答复: low memory killer On Thu 20-11-14 10:09:25, zhiyuan_zhu@xxxxxxx wrote: > Hi Michal > Thanks for your kindly support. > I got a device, and dump the /proc/meminfo and /proc/vmstat files, > they are the Linux standard proc files. > I found that: Cached = 339880 KB, but nr_free_pages=14675*4 = 58700KB > and nr_shmem = 508*4=2032KB > > nr_shmem is just a little memory, and nr free pages + nr_shmem is > largely less than Cached. So why nr_free_pages is largely less than > Cached? Thank you. nr_free_pages refers to pages which are not allocated. Cached referes to a used memory which is easily reclaimable so it can be reused should there be a need and free memory drops down. So this is a normal situation. How is this related to the lowmemory killer question posted previously? [...] -- Michal Hocko SUSE Labs
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