From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f50.google.com (mail-oi0-f50.google.com [209.85.218.50]) by kanga.kvack.org (Postfix) with ESMTP id 11CDE6B0038 for ; Tue, 5 May 2015 09:55:55 -0400 (EDT) Received: by oica37 with SMTP id a37so146582034oic.0 for ; Tue, 05 May 2015 06:55:54 -0700 (PDT) Received: from g2t2352.austin.hp.com (g2t2352.austin.hp.com. [15.217.128.51]) by mx.google.com with ESMTPS id f1si10206305obh.88.2015.05.05.06.55.54 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 May 2015 06:55:54 -0700 (PDT) Message-ID: <5548CBE8.5090203@hp.com> Date: Tue, 05 May 2015 09:55:52 -0400 From: Waiman Long MIME-Version: 1.0 Subject: Re: [PATCH 0/13] Parallel struct page initialisation v4 References: <1430231830-7702-1-git-send-email-mgorman@suse.de> <554030D1.8080509@hp.com> <5543F802.9090504@hp.com> <554415B1.2050702@hp.com> <20150504143046.9404c572486caf71bdef0676@linux-foundation.org> <20150505104514.GC2462@suse.de> In-Reply-To: <20150505104514.GC2462@suse.de> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrew Morton , Nathan Zimmer , Dave Hansen , Scott Norton , Daniel J Blueman , Linux-MM , LKML On 05/05/2015 06:45 AM, Mel Gorman wrote: > On Mon, May 04, 2015 at 02:30:46PM -0700, Andrew Morton wrote: >>> Before the patch, the boot time from elilo prompt to ssh login was 694s. >>> After the patch, the boot up time was 346s, a saving of 348s (about 50%). >> Having to guesstimate the amount of memory which is needed for a >> successful boot will be painful. Any number we choose will be wrong >> 99% of the time. >> >> If the kswapd threads have started, all we need to do is to wait: take >> a little nap in the allocator's page==NULL slowpath. >> >> I'm not seeing any reason why we can't start kswapd much earlier - >> right at the start of do_basic_setup()? > It doesn't even have to be kswapd, it just should be a thread pinned to > a done. The difficulty is that dealing with the system hashes means the > initialisation has to happen before vfs_caches_init_early() when there is > no scheduler. Those allocations could be delayed further but then there is > the possibility that the allocations would not be contiguous and they'd > have to rely on CMA to make the attempt. That potentially alters the > performance of the large system hashes at run time. > > We can scale the amount initialised with memory sizes relatively easy. > This boots on the same 1TB machine I was testing before but that is > hardly a surprise. > > ---8<--- > mm: meminit: Take into account that large system caches scale linearly with memory > > Waiman Long reported a 24TB machine triggered an OOM as parallel memory > initialisation deferred too much memory for initialisation. The likely > consumer of this memory was large system hashes that scale with memory > size. This patch initialises at least 2G per node but scales the amount > initialised for larger systems. > > Signed-off-by: Mel Gorman > --- > mm/page_alloc.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 598f78d6544c..f7cc6c9fb909 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -266,15 +266,16 @@ static inline bool early_page_nid_uninitialised(unsigned long pfn, int nid) > */ > static inline bool update_defer_init(pg_data_t *pgdat, > unsigned long pfn, unsigned long zone_end, > + unsigned long max_initialise, > unsigned long *nr_initialised) > { > /* Always populate low zones for address-contrained allocations */ > if (zone_end< pgdat_end_pfn(pgdat)) > return true; > > - /* Initialise at least 2G of the highest zone */ > + /* Initialise at least the requested amount in the highest zone */ > (*nr_initialised)++; > - if (*nr_initialised> (2UL<< (30 - PAGE_SHIFT))&& > + if ((*nr_initialised> max_initialise)&& > (pfn& (PAGES_PER_SECTION - 1)) == 0) { > pgdat->first_deferred_pfn = pfn; > return false; > @@ -299,6 +300,7 @@ static inline bool early_page_nid_uninitialised(unsigned long pfn, int nid) > > static inline bool update_defer_init(pg_data_t *pgdat, > unsigned long pfn, unsigned long zone_end, > + unsigned long max_initialise, > unsigned long *nr_initialised) > { > return true; > @@ -4457,11 +4459,19 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, > unsigned long end_pfn = start_pfn + size; > unsigned long pfn; > struct zone *z; > + unsigned long max_initialise; > unsigned long nr_initialised = 0; > > if (highest_memmap_pfn< end_pfn - 1) > highest_memmap_pfn = end_pfn - 1; > > + /* > + * Initialise at least 2G of a node but also take into account that > + * two large system hashes that can take up an 8th of memory. > + */ > + max_initialise = min(2UL<< (30 - PAGE_SHIFT), > + (pgdat->node_spanned_pages>> 3)); > + I think you may be pre-allocating too much memory here. On the 24-TB machine, the size of the dentry and inode hash tables were 16G each. So the ratio is about is about 32G/24T = 0.13%. I think a shift factor of (>> 8) which is about 0.39% should be more than enough. For the 24TB machine, that means a preallocated memory of 96+4G which should be even more than the 64+4G in the modified kernel that I used. At the same time, I think we can also set the minimum to 1G or even 0.5G for better performance for systems that have many CPUs, but not as much memory per node. Cheers, Longman -- 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/ . Don't email: email@kvack.org