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From: David Miller <davem@davemloft.net>
To: mhocko@kernel.org
Cc: pasha.tatashin@oracle.com, linux-kernel@vger.kernel.org,
	sparclinux@vger.kernel.org, linux-mm@kvack.org,
	linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
	borntraeger@de.ibm.com, heiko.carstens@de.ibm.com
Subject: Re: [v3 0/9] parallelized "struct page" zeroing
Date: Wed, 31 May 2017 12:51:18 -0400 (EDT)	[thread overview]
Message-ID: <20170531.125118.94140984076231176.davem@davemloft.net> (raw)
In-Reply-To: <20170531163131.GY27783@dhcp22.suse.cz>

From: Michal Hocko <mhocko@kernel.org>
Date: Wed, 31 May 2017 18:31:31 +0200

> On Tue 30-05-17 13:16:50, Pasha Tatashin wrote:
>> >Could you be more specific? E.g. how are other stores done in
>> >__init_single_page safe then? I am sorry to be dense here but how does
>> >the full 64B store differ from other stores done in the same function.
>> 
>> Hi Michal,
>> 
>> It is safe to do regular 8-byte and smaller stores (stx, st, sth, stb)
>> without membar, but they are slower compared to STBI which require a membar
>> before memory can be accessed.
> 
> OK, so why cannot we make zero_struct_page 8x 8B stores, other arches
> would do memset. You said it would be slower but would that be
> measurable? I am sorry to be so persistent here but I would be really
> happier if this didn't depend on the deferred initialization. If this is
> absolutely a no-go then I can live with that of course.

It is measurable.  That's the impetus for this work in the first place.

When the do the memory barrier, the whole store buffer flushes because
the memory barrier is done with a dependency on the next load or store
operation, one of which the caller is going to do immediately.

  reply	other threads:[~2017-05-31 16:51 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-05 17:03 [v3 0/9] parallelized "struct page" zeroing Pavel Tatashin
2017-05-05 17:03 ` [v3 1/9] sparc64: simplify vmemmap_populate Pavel Tatashin
2017-05-05 17:03 ` [v3 2/9] mm: defining memblock_virt_alloc_try_nid_raw Pavel Tatashin
2017-05-05 17:03 ` [v3 3/9] mm: add "zero" argument to vmemmap allocators Pavel Tatashin
2017-05-13 19:17   ` kbuild test robot
2017-05-05 17:03 ` [v3 4/9] mm: do not zero vmemmap_buf Pavel Tatashin
2017-05-05 17:03 ` [v3 5/9] mm: zero struct pages during initialization Pavel Tatashin
2017-05-05 17:03 ` [v3 6/9] sparc64: teach sparc not to zero struct pages memory Pavel Tatashin
2017-05-05 17:03 ` [v3 7/9] x86: teach x86 " Pavel Tatashin
2017-05-05 17:03 ` [v3 8/9] powerpc: teach platforms " Pavel Tatashin
2017-05-05 17:03 ` [v3 9/9] s390: " Pavel Tatashin
2017-05-08 11:36   ` Heiko Carstens
2017-05-15 18:24     ` Pasha Tatashin
2017-05-15 23:17       ` Heiko Carstens
2017-05-16  0:33         ` Pasha Tatashin
2017-05-09 18:12 ` [v3 0/9] parallelized "struct page" zeroing Michal Hocko
2017-05-09 18:54   ` Pasha Tatashin
2017-05-10  7:24     ` Michal Hocko
2017-05-10 13:42       ` Pasha Tatashin
2017-05-10 14:57         ` Michal Hocko
2017-05-10 15:01           ` Pasha Tatashin
2017-05-10 15:20             ` David Miller
2017-05-11 20:47             ` Pasha Tatashin
2017-05-11 20:59               ` Pasha Tatashin
2017-05-12 16:57                 ` David Miller
2017-05-12 17:24                   ` Pasha Tatashin
2017-05-12 17:37                     ` David Miller
2017-05-16 23:50                       ` Benjamin Herrenschmidt
2017-05-12 16:56               ` David Miller
2017-05-10 15:19           ` David Miller
2017-05-10 17:17             ` Matthew Wilcox
2017-05-10 18:00               ` David Miller
2017-05-10 21:11                 ` Matthew Wilcox
2017-05-11  8:05             ` Michal Hocko
2017-05-11 14:35               ` David Miller
2017-05-15 18:12   ` Pasha Tatashin
2017-05-15 19:38     ` Michal Hocko
2017-05-15 20:44       ` Pasha Tatashin
2017-05-16  8:36         ` Michal Hocko
2017-05-26 16:45           ` Pasha Tatashin
2017-05-29 11:53             ` Michal Hocko
2017-05-30 17:16               ` Pasha Tatashin
2017-05-31 16:31                 ` Michal Hocko
2017-05-31 16:51                   ` David Miller [this message]
2017-06-01  3:35                   ` Pasha Tatashin
2017-06-01  8:46                     ` Michal Hocko

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