linux-kernel - Re: [PATCH v1] kernel/trace:check the val against the available mem

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Message-ID: <20180404152713.GM6312@dhcp22.suse.cz>
Date:   Wed, 4 Apr 2018 17:27:13 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Zhaoyang Huang <huangzhaoyang@...il.com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        kernel-patch-test@...ts.linaro.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joel Fernandes <joelaf@...gle.com>, linux-mm@...ck.org,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v1] kernel/trace:check the val against the available mem

On Wed 04-04-18 11:04:42, Steven Rostedt wrote:
[...]
> I'm not looking for perfect. In fact, I love what si_mem_available()
> gives me now! Sure, it can say "there's enough memory" even if I can't
> use it. Because most of the OOM allocations that happen with increasing
> the size of the ring buffer isn't due to "just enough memory
> allocated", but it's due to "trying to allocate crazy amounts of
> memory".  That's because it does the allocation one page at a time, and
> if you try to allocate crazy amounts of memory, it will allocate all
> memory before it fails. I don't want that. I want crazy allocations to
> fail from the start. A "maybe this will allocate" is fine even if it
> will end up causing an OOM.

OK, fair enough. It's your code ;) I would recommend using the
oom_origin thingy to reduce the immediate damage and to have a clear
culprit so that I do not have to scratch my head why we see an OOM
report with a lot of unaccounted memory...

I am afraid I cannot help you much more though.
-- 
Michal Hocko
SUSE Labs