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From: David Rientjes <rientjes@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: Re: [PATCH] mm:memcg: add __GFP_NOWARN in __memcg_schedule_kmem_cache_create
Date: Tue, 17 Apr 2018 21:16:42 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.21.1804172113400.114494@chino.kir.corp.google.com> (raw)
In-Reply-To: <20180418030824.GA7320@bombadil.infradead.org>

On Tue, 17 Apr 2018, Matthew Wilcox wrote:

> Not arguing against this patch.  But how many places do we want to use
> GFP_NOWAIT without __GFP_NOWARN?  Not many, and the few which do do this
> seem like they simply haven't added it yet.  Maybe this would be a good idea?
> 
> -#define GFP_NOWAIT      (__GFP_KSWAPD_RECLAIM)
> +#define GFP_NOWAIT      (__GFP_KSWAPD_RECLAIM | __GFP_NOWARN)
> 

I don't think that's a good idea, slab allocators use GFP_NOWAIT during 
init, for example, followed up with a BUG_ON() if it fails.  With an 
implicit __GFP_NOWARN we wouldn't be able to see the state of memory when 
it crashes (likely memory that wasn't freed to the allocator).  I think 
whether the allocation failure should trigger a warning is up to the 
caller.

  reply	other threads:[~2018-04-18  4:16 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18  2:29 [PATCH] mm:memcg: add __GFP_NOWARN in __memcg_schedule_kmem_cache_create Minchan Kim
2018-04-18  2:56 ` David Rientjes
2018-04-18  3:08 ` Matthew Wilcox
2018-04-18  4:16   ` David Rientjes [this message]
2018-04-18  7:09   ` Michal Hocko
2018-04-18  7:20 ` Michal Hocko
2018-04-18  7:41   ` Minchan Kim
2018-04-18  7:54     ` Michal Hocko
2018-04-18 13:23       ` Minchan Kim
2018-04-18 13:27         ` Michal Hocko
2018-04-18 18:58           ` David Rientjes
2018-04-19  6:40             ` Michal Hocko
2018-04-20  5:42               ` Minchan Kim
2018-04-20  8:09                 ` Michal Hocko
2018-04-18 13:31 ` Matthew Wilcox
2018-04-18 13:39   ` Michal Hocko
2018-04-18 19:05 ` Johannes Weiner

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