From: Michal Hocko <mhocko@kernel.org>
To: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Steve Sistare <steven.sistare@oracle.com>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
mgorman@techsingularity.net,
Linux Memory Management List <linux-mm@kvack.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/1] mm: buddy page accessed before initialized
Date: Fri, 3 Nov 2017 14:53:49 +0100 [thread overview]
Message-ID: <20171103135349.gsotgdjwo5sqe47y@dhcp22.suse.cz> (raw)
In-Reply-To: <CAOAebxvXz2+N36QLo5xdJzbCfCPeC5E3a1p0PBTtN5ZXNNYG8Q@mail.gmail.com>
On Fri 03-11-17 09:47:30, Pavel Tatashin wrote:
> Hi Michal,
>
> There is a small regression, on the largest x86 machine I have access to:
> Before:
> node 1 initialised, 32471632 pages in 901ms
> After:
> node 1 initialised, 32471632 pages in 1128ms
>
> One node contains 128G of memory (overal 1T in 8 nodes). This
> regression is going to be solved by this work:
> https://patchwork.kernel.org/patch/9920953/, other than that I do not
> know a better solution. The overall performance is still much better
> compared to before this project.
OK, I think that is completely acceptable for now. We can always
optimize for a better result later.
> Also, thinking about this problem some more, it is safer to split the
> initialization, and freeing parts into two functions:
>
> In deferred_init_memmap()
> 1574 for_each_free_mem_range(i, nid, MEMBLOCK_NONE, &spa, &epa, NULL) {
> 1575 spfn = max_t(unsigned long, first_init_pfn, PFN_UP(spa));
> 1576 epfn = min_t(unsigned long, zone_end_pfn(zone),
> PFN_DOWN(epa));
> 1577 nr_pages += deferred_init_range(nid, zid, spfn, epfn);
> 1578 }
>
> Replace with two loops:
> First loop, calls a function that initializes the given range, the 2nd
> loop calls a function that frees it. This way we won't get a potential
> problem where buddy page is computed from the next range that has not
> yet been initialized. And it is also going to be easier to multithread
> later: multi-thread the first loop, wait for it to finish,
> multi-thread the 2nd loop wait for it to finish.
OK, but let's do that as a separate patch. What you have here is good
for now IMHO. My ack applies. Thanks!
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2017-11-03 13:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-02 17:02 [PATCH v2 0/1] mm: buddy page accessed before initialized Pavel Tatashin
2017-11-02 17:02 ` [PATCH v2 1/1] " Pavel Tatashin
2017-11-03 9:27 ` Michal Hocko
2017-11-03 13:47 ` Pavel Tatashin
2017-11-03 13:53 ` Michal Hocko [this message]
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