linux-kernel - Re: [RFC PATCH] mm, page_alloc: drop should_suppress_show

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Message-ID: <188ef8c6-262c-cead-6f78-ebda0978cce6@suse.cz>
Date:   Fri, 7 Sep 2018 14:16:16 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [RFC PATCH] mm, page_alloc: drop should_suppress_show_mem

On 09/07/2018 01:43 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> should_suppress_show_mem has been introduced to reduce the overhead of
> show_mem on large NUMA systems. Things have changed since then though.
> Namely c78e93630d15 ("mm: do not walk all of system memory during
> show_mem") has reduced the overhead considerably.
> 
> Moreover warn_alloc_show_mem clears SHOW_MEM_FILTER_NODES when called
> from the IRQ context already so we are not printing per node stats.
> 
> Remove should_suppress_show_mem because we are losing potentially
> interesting information about allocation failures. We have seen a bug
> report where system gets unresponsive under memory pressure and there
> is only
> kernel: [2032243.696888] qlge 0000:8b:00.1 ql1: Could not get a page chunk, i=8, clean_idx =200 .
> kernel: [2032243.710725] swapper/7: page allocation failure: order:1, mode:0x1084120(GFP_ATOMIC|__GFP_COLD|__GFP_COMP)
> 
> without an additional information for debugging. It would be great to
> see the state of the page allocator at the moment.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

The dependency on build-time constant instead of real system size is
also unfortunate. Maybe the time was depending on *possible* nodes in
the past, but I don't think it's the case today.

Thanks.