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

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Message-ID: <20180405103050.22f10319@gandalf.local.home>
Date:   Thu, 5 Apr 2018 10:30:50 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Joel Fernandes <joelaf@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Zhaoyang Huang <huangzhaoyang@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-patch-test@...ts.linaro.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v1] kernel/trace:check the val against the available mem

On Thu, 5 Apr 2018 07:22:58 -0700
Matthew Wilcox <willy@...radead.org> wrote:

> I understand you don't want GFP_NORETRY.  But why is it more important for
> this allocation to succeed than other normal GFP_KERNEL allocations?

Not sure what you mean by "more important"? Does saying "RETRY_MAYFAIL"
make it more important? The difference is, if GFP_KERNEL fails, we
don't want to trigger an OOM, and simply clean up and report -ENOMEM to
the user. It has nothing to do with being more important than other
allocations.

If there's 100 Megs of memory available, and the user requests a gig of
memory, it's going to fail. Ideally, it doesn't trigger OOM, but
instead simply reports -ENOMEM to the user.

-- Steve