From: Steven Rostedt <rostedt@goodmis.org>
To: Joel Fernandes <joelaf@google.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Zhaoyang Huang <huangzhaoyang@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-patch-test@lists.linaro.org,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
Vlastimil Babka <vbabka@suse.cz>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v1] kernel/trace:check the val against the available mem
Date: Fri, 30 Mar 2018 21:41:51 -0400 [thread overview]
Message-ID: <20180330214151.415e90ea@gandalf.local.home> (raw)
In-Reply-To: <CAJWu+orx=NZrkAf7x_HqttnrMssmW7DPZOL1fxR=N6D_-fbmtw@mail.gmail.com>
On Fri, 30 Mar 2018 16:38:52 -0700
Joel Fernandes <joelaf@google.com> wrote:
> > --- a/kernel/trace/ring_buffer.c
> > +++ b/kernel/trace/ring_buffer.c
> > @@ -1164,6 +1164,11 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
> > struct buffer_page *bpage, *tmp;
> > long i;
> >
> > + /* Check if the available memory is there first */
> > + i = si_mem_available();
> > + if (i < nr_pages)
>
> Does it make sense to add a small margin here so that after ftrace
> finishes allocating, we still have some memory left for the system?
> But then then we have to define a magic number :-|
I don't think so. The memory is allocated by user defined numbers. They
can do "free" to see what is available. The original patch from
Zhaoyang was due to a script that would just try a very large number
and cause issues.
If the memory is available, I just say let them have it. This is
borderline user space issue and not a kernel one.
> > +
>
> I tested in Qemu with 1GB memory, I am always able to get it to fail
> allocation even without this patch without causing an OOM. Maybe I am
> not running enough allocations in parallel or something :)
Try just echoing in "1000000" into buffer_size_kb and see what happens.
>
> The patch you shared using si_mem_available is working since I'm able
> to allocate till the end without a page allocation failure:
>
> bash-4.3# echo 237800 > /d/tracing/buffer_size_kb
> bash: echo: write error: Cannot allocate memory
> bash-4.3# echo 237700 > /d/tracing/buffer_size_kb
> bash-4.3# free -m
> total used free shared buffers
> Mem: 985 977 7 10 0
> -/+ buffers: 977 7
> Swap: 0 0 0
> bash-4.3#
>
> I think this patch is still good to have, since IMO we should not go
> and get page allocation failure (even if its a non-OOM) and subsequent
> stack dump from mm's allocator, if we can avoid it.
>
> Tested-by: Joel Fernandes <joelaf@google.com>
Great thanks! I'll make it into a formal patch.
-- Steve
next prev parent reply other threads:[~2018-03-31 1:41 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-29 10:41 [PATCH v1] kernel/trace:check the val against the available mem 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 [this message]
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
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
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