From: Hugh Dickins <hughd@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Nick Piggin <npiggin@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Bob Peterson <rpeterso@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Steven Whitehouse <swhiteho@redhat.com>,
Andrew Lutomirski <luto@kernel.org>,
Andreas Gruenbacher <agruenba@redhat.com>,
Mel Gorman <mgorman@techsingularity.net>,
linux-mm <linux-mm@kvack.org>
Subject: Re: [RFC][PATCH] make global bitlock waitqueues per-node
Date: Thu, 22 Dec 2016 11:28:31 -0800 (PST) [thread overview]
Message-ID: <alpine.LSU.2.11.1612221120230.4215@eggly.anvils> (raw)
In-Reply-To: <CA+55aFx-YmpZ4NBU0oSw_iJV8jEMaL8qX-HCH=DrutQ65UYR5A@mail.gmail.com>
On Wed, 21 Dec 2016, Linus Torvalds wrote:
> On Wed, Dec 21, 2016 at 12:32 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > FWIW, here's mine.. compiles and boots on a NUMA x86_64 machine.
>
> So I like how your patch is smaller, but your patch is also broken.
>
> First off, the whole contention bit is *not* NUMA-specific. It should
> help non-NUMA too, by avoiding the stupid extra cache miss.
>
> Secondly, CONFIG_NUMA is a broken thing to test anyway, since adding a
> bit for the NUMA case can overflow the page flags as far as I can tell
> (MIPS seems to support NUMA on 32-bit, for example, but I didn't
> really check the Kconfig details). Making it dependent on 64-bit might
> be ok (and would fix the issue above - I don't think we really need to
> care too much about 32-bit any more)
>
> But making it conditional at all means that now you have those two
> different cases for this, which is a maintenance nightmare. So don't
> do it even if we could say "screw 32-bit".
>
> Anyway, the conditional thing could be fixed by just taking Nick's
> patch 1/2, and your patch (with the conditional bits stripped out).
Yup.
>
> I do think your approach of just re-using the existing bit waiting
> with just a page-specific waiting function is nicer than Nick's "let's
> just roll new waiting functions" approach. It also avoids the extra
> initcall.
>
> Nick, comments?
>
> Hugh - mind testing PeterZ's patch too? My comments about the
> conditional PG_waiters bit and page bit overflow are not relevant for
> your particular scenario, so you can ignore that part, and just take
> PaterZ's patch directly.
Right, I put them both through some loads yesterday and overnight:
Peter's patch and Nick's patch each work fine here, no issues seen
with either (but I didn't attempt to compare them, aesthetically
nor in performance).
Hugh
next prev parent reply other threads:[~2016-12-22 19:28 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-19 22:58 [RFC][PATCH] make global bitlock waitqueues per-node Dave Hansen
[not found] ` <CA+55aFwK6JdSy9v_BkNYWNdfK82sYA1h3qCSAJQ0T45cOxeXmQ@mail.gmail.com>
2016-12-20 0:20 ` Dave Hansen
2016-12-20 2:31 ` Nicholas Piggin
2016-12-20 12:58 ` Mel Gorman
2016-12-20 13:21 ` Nicholas Piggin
2016-12-20 17:31 ` Linus Torvalds
2016-12-20 18:02 ` Linus Torvalds
2016-12-21 8:09 ` Peter Zijlstra
2016-12-21 8:32 ` Peter Zijlstra
2016-12-21 18:02 ` Linus Torvalds
2016-12-21 18:33 ` Nicholas Piggin
2016-12-21 19:01 ` Nicholas Piggin
2016-12-21 19:50 ` Linus Torvalds
2016-12-22 2:07 ` Nicholas Piggin
2016-12-22 19:28 ` Hugh Dickins [this message]
2016-12-21 10:26 ` Nicholas Piggin
2016-12-20 2:26 ` Nicholas Piggin
2016-12-21 12:30 ` Nicholas Piggin
2016-12-21 18:12 ` Linus Torvalds
2016-12-21 18:40 ` Nicholas Piggin
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