From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: Regression from 2.6.36 Date: Wed, 13 Apr 2011 14:54:40 -0700 Message-ID: <20110413145440.f81f30ed.akpm@linux-foundation.org> References: <20110315132527.130FB80018F1@mail1005.cent> <20110317001519.GB18911@kroah.com> <20110407120112.E08DCA03@pobox.sk> <4D9D8FAA.9080405@suse.cz> <1302177428.3357.25.camel@edumazet-laptop> <1302178426.3357.34.camel@edumazet-laptop> <1302190586.3357.45.camel@edumazet-laptop> <20110412154906.70829d60.akpm@linux-foundation.org> <20110412183132.a854bffc.akpm@linux-foundation.org> <1302662256.2811.27.camel@edumazet-laptop> <20110413141600.28793661.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , Changli Gao , =?ISO-8859-1?Q?Am=E9rico?= Wang , Jiri Slaby , azurIt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Jiri Slaby , Mel Gorman , Christoph Lameter To: David Rientjes Return-path: In-Reply-To: Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Wed, 13 Apr 2011 14:44:16 -0700 (PDT) David Rientjes wrote: > > -static inline void *alloc_fdmem(unsigned int size) > > +static void *alloc_fdmem(unsigned int size) > > { > > - void *data; > > - > > - data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN); > > - if (data != NULL) > > - return data; > > - > > + /* > > + * Very large allocations can stress page reclaim, so fall back to > > + * vmalloc() if the allocation size will be considered "large" by the VM. > > + */ > > + if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) { > > + void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN); > > + if (data != NULL) > > + return data; > > + } > > return vmalloc(size); > > } > > > > It's a shame that we can't at least try kmalloc() with sufficiently large > sizes by doing something like > > gfp_t flags = GFP_NOWAIT | __GFP_NOWARN; > > if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) > flags |= GFP_KERNEL; > data = kmalloc(size, flags); > if (data) > return data; > return vmalloc(size); > > which would at least attempt to use the slab allocator. Maybe. If the fdtable is that huge then the fork() is probably going to be pretty slow anyway. And the large allocation might cause depletion of high-order free pages and might cause fragmentation of even-higher-order pages by splitting them up. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org