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Subject: Re: [PATCH] Add slowpath enter/exit trace events
References: <20171123104336.25855-1-peter.enderborg@sony.com>
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Message-ID: <f12576a9-93e5-48db-3e70-88d73907801d@I-love.SAKURA.ne.jp>
Date: Thu, 23 Nov 2017 22:00:04 +0900
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To: peter.enderborg@sony.com, Michal Hocko <mhocko@suse.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>, Alex Deucher <alexander.deucher@amd.com>, "David S . Miller" <davem@davemloft.net>, Harry Wentland <Harry.Wentland@amd.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Tony Cheng <Tony.Cheng@amd.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Mel Gorman <mgorman@techsingularity.net>, Johannes Weiner <hannes@cmpxchg.org>, Pavel Tatashin <pasha.tatashin@oracle.com>

On 2017/11/23 19:43, peter.enderborg@sony.com wrote:
> The warning of slow allocation has been removed, this is
> a other way to fetch that information. But you need
> to enable the trace. The exit function also returns
> information about the number of retries, how long
> it was stalled and failure reason if that happened.

However, the fast path (I mean, get_page_from_freelist() at
"/* First allocation attempt */" label) might be slow, for it is
allowed to call node_reclaim() which can take uncontrollable
duration. I think that you need to add hooks like
http://lkml.kernel.org/r/1510833448-19918-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp does. ;-)

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