LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Michal Hocko <mhocko@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Zhaoyang Huang <huangzhaoyang@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	linux-kernel@vger.kernel.org, kernel-patch-test@lists.linaro.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Joel Fernandes <joelaf@google.com>,
	linux-mm@kvack.org, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v1] kernel/trace:check the val against the available mem
Date: Tue, 3 Apr 2018 13:06:12 +0200
Message-ID: <20180403110612.GM5501@dhcp22.suse.cz> (raw)
In-Reply-To: <20180330102038.2378925b@gandalf.local.home>

On Fri 30-03-18 10:20:38, Steven Rostedt wrote:
> 
> [ Adding memory management folks to discuss the issue ]
> 
> On Thu, 29 Mar 2018 18:41:44 +0800
> Zhaoyang Huang <huangzhaoyang@gmail.com> wrote:
> 
> > It is reported that some user app would like to echo a huge
> > number to "/sys/kernel/debug/tracing/buffer_size_kb" regardless
> >  of the available memory, which will cause the coinstantaneous
> > page allocation failed and introduce OOM. The commit checking the
> > val against the available mem first to avoid the consequence allocation.
> > 
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@spreadtrum.com>
> > ---
> >  kernel/trace/trace.c | 39 ++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 38 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 2d0ffcc..a4a4237 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -43,6 +43,8 @@
> >  #include <linux/trace.h>
> >  #include <linux/sched/rt.h>
> >  
> > +#include <linux/mm.h>
> > +#include <linux/swap.h>
> >  #include "trace.h"
> >  #include "trace_output.h"
> >  
> > @@ -5967,6 +5969,39 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
> >  	return ret;
> >  }
> >  
> > +static long get_available_mem(void)
> > +{
> > +	struct sysinfo i;
> > +	long available;
> > +	unsigned long pagecache;
> > +	unsigned long wmark_low = 0;
> > +	unsigned long pages[NR_LRU_LISTS];
> > +	struct zone *zone;
> > +	int lru;
> > +
> > +	si_meminfo(&i);
> > +	si_swapinfo(&i);
> > +
> > +	for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++)
> > +		pages[lru] = global_page_state(NR_LRU_BASE + lru);
> > +
> > +	for_each_zone(zone)
> > +		wmark_low += zone->watermark[WMARK_LOW];
> > +
> > +	available = i.freeram - wmark_low;
> > +
> > +	pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE];
> > +	pagecache -= min(pagecache / 2, wmark_low);
> > +	available += pagecache;
> > +
> > +	available += global_page_state(NR_SLAB_RECLAIMABLE) -
> > +		min(global_page_state(NR_SLAB_RECLAIMABLE) / 2, wmark_low);
> > +
> > +	if (available < 0)
> > +		available = 0;
> > +	return available;
> > +}
> > +
> 
> As I stated in my other reply, the above function does not belong in
> tracing.
> 
> That said, it appears you are having issues that were caused by the
> change by commit 848618857d2 ("tracing/ring_buffer: Try harder to
> allocate"), where we replaced NORETRY with RETRY_MAYFAIL. The point of
> NORETRY was to keep allocations of the tracing ring-buffer from causing
> OOMs. But the RETRY was too strong in that case, because there were
> those that wanted to allocate large ring buffers but it would fail due
> to memory being used that could be reclaimed. Supposedly, RETRY_MAYFAIL
> is to allocate with reclaim but still allow to fail, and isn't suppose
> to trigger an OOM. From my own tests, this is obviously not the case.
> 
> Perhaps this is because the ring buffer allocates one page at a time,
> and by doing so, it can get every last available page, and if anything
> in the mean time does an allocation without MAYFAIL, it will cause an
> OOM. For example, when I stressed this I triggered this:

Yes, this is indeed the case.

>  pool invoked oom-killer: gfp_mask=0x14200ca(GFP_HIGHUSER_MOVABLE), nodemask=(null), order=0, oom_score_adj=0
>  pool cpuset=/ mems_allowed=0
>  CPU: 7 PID: 1040 Comm: pool Not tainted 4.16.0-rc4-test+ #663
>  Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016
>  Call Trace:
>   dump_stack+0x8e/0xce
>   dump_header.isra.30+0x6e/0x28f
>   ? _raw_spin_unlock_irqrestore+0x30/0x60
>   oom_kill_process+0x218/0x400
>   ? has_capability_noaudit+0x17/0x20
>   out_of_memory+0xe3/0x5c0
>   __alloc_pages_slowpath+0xa8e/0xe50
>   __alloc_pages_nodemask+0x206/0x220
>   alloc_pages_current+0x6a/0xe0
>   __page_cache_alloc+0x6a/0xa0
>   filemap_fault+0x208/0x5f0
>   ? __might_sleep+0x4a/0x80
>   ext4_filemap_fault+0x31/0x44
>   __do_fault+0x20/0xd0
>   __handle_mm_fault+0xc08/0x1160
>   handle_mm_fault+0x76/0x110
>   __do_page_fault+0x299/0x580
>   do_page_fault+0x2d/0x110
>   ? page_fault+0x2f/0x50
>   page_fault+0x45/0x50
> 
> I wonder if I should have the ring buffer allocate groups of pages, to
> avoid this. Or try to allocate with NORETRY, one page at a time, and
> when that fails, allocate groups of pages with RETRY_MAYFAIL, and that
> may keep it from causing an OOM?

I wonder why it really matters. The interface is root only and we expect
some sanity from an admin, right? So allocating such a large ring buffer
that it sends the system to the OOM is a sign that the admin should be
more careful. Balancing on the OOM edge is always a risk and the result
will highly depend on the workload running in parallel.
-- 
Michal Hocko
SUSE Labs

  parent reply index

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-29 10:41 Zhaoyang Huang
2018-03-29 16:05 ` Steven Rostedt
2018-03-30  3:32   ` Zhaoyang Huang
2018-03-30 14:07     ` Steven Rostedt
2018-03-30  6:53 ` [Kernel-patch-test] " kbuild test robot
2018-03-30  6:54 ` kbuild test robot
2018-03-30 14:20 ` Steven Rostedt
2018-03-30 16:37   ` Joel Fernandes
2018-03-30 19:10     ` Steven Rostedt
2018-03-30 20:37       ` Joel Fernandes
2018-03-30 20:53   ` Matthew Wilcox
2018-03-30 21:30     ` Steven Rostedt
2018-03-30 21:42       ` Steven Rostedt
2018-03-30 23:38         ` Joel Fernandes
2018-03-31  1:41           ` Steven Rostedt
2018-03-31  2:18             ` Matthew Wilcox
2018-03-31  3:07               ` Steven Rostedt
2018-03-31  5:44                 ` Joel Fernandes
2018-04-02  0:52         ` Zhaoyang Huang
2018-04-03 11:06   ` Michal Hocko [this message]
2018-04-03 11:51     ` Steven Rostedt
2018-04-03 12:16       ` Michal Hocko
2018-04-03 12:23         ` Steven Rostedt
2018-04-03 12:35           ` Michal Hocko
2018-04-03 13:32             ` Steven Rostedt
2018-04-03 13:56               ` Michal Hocko
2018-04-03 14:17                 ` Steven Rostedt
2018-04-03 16:11                   ` Michal Hocko
2018-04-03 16:59                     ` Steven Rostedt
2018-04-03 22:56                     ` Steven Rostedt
2018-04-04  6:20                       ` Michal Hocko
2018-04-04 12:21                         ` Joel Fernandes
2018-04-04 12:59                         ` Steven Rostedt
2018-04-04 14:10                           ` Michal Hocko
2018-04-04 14:25                             ` Steven Rostedt
2018-04-04 14:42                               ` Michal Hocko
2018-04-04 15:04                                 ` Steven Rostedt
2018-04-04 15:27                                   ` Michal Hocko
2018-04-04 15:38                                     ` Steven Rostedt
2018-04-04  2:58                 ` Zhaoyang Huang
2018-04-04  6:23                   ` Michal Hocko
2018-04-04  9:29                     ` Zhaoyang Huang
2018-04-04 14:11                     ` Steven Rostedt
2018-04-04 14:23                       ` Michal Hocko
2018-04-04 14:31                         ` Steven Rostedt
2018-04-04 14:47                           ` Michal Hocko
2018-04-04 15:47                         ` Steven Rostedt
2018-04-05  2:58                           ` Matthew Wilcox
2018-04-05  4:12                             ` Joel Fernandes
2018-04-05 14:22                               ` Matthew Wilcox
2018-04-05 14:27                                 ` Michal Hocko
2018-04-05 14:34                                   ` Steven Rostedt
2018-04-05 15:13                                   ` Matthew Wilcox
2018-04-05 15:32                                     ` Michal Hocko
2018-04-05 16:15                                       ` Matthew Wilcox
2018-04-05 18:54                                         ` Michal Hocko
2018-04-05 20:15                                           ` __GFP_LOW Matthew Wilcox
2018-04-06  6:09                                             ` __GFP_LOW Michal Hocko
2018-04-08  4:27                                               ` __GFP_LOW Matthew Wilcox
2018-04-09  7:34                                                 ` __GFP_LOW Michal Hocko
2018-04-09 15:51                                                   ` __GFP_LOW Matthew Wilcox
2018-04-09 18:14                                                     ` __GFP_LOW Michal Hocko
     [not found]                                                       ` <CA+JonM0HG9kWb6-0iyDQ8UMxTeR-f=+ZL89t5DvvDULDC8Sfyw@mail.gmail.com>
2018-04-10 12:19                                                         ` __GFP_LOW Matthew Wilcox
2018-04-05 14:30                                 ` [PATCH v1] kernel/trace:check the val against the available mem Steven Rostedt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180403110612.GM5501@dhcp22.suse.cz \
    --to=mhocko@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=huangzhaoyang@gmail.com \
    --cc=joelaf@google.com \
    --cc=kernel-patch-test@lists.linaro.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mingo@kernel.org \
    --cc=rostedt@goodmis.org \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git
	git clone --mirror https://lore.kernel.org/lkml/10 lkml/git/10.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git