From: Dave Hansen <dave@sr71.net>
To: Will Deacon <will.deacon@arm.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Peter Zijlstra <peterz@infradead.org>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Michal Simek <monstr@monstr.eu>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: post-3.18 performance regression in TLB flushing code
Date: Wed, 17 Dec 2014 10:52:02 -0800 [thread overview]
Message-ID: <5491D0D2.5070103@sr71.net> (raw)
In-Reply-To: <20141217165310.GJ870@arm.com>
On 12/17/2014 08:53 AM, Will Deacon wrote:
> On Wed, Dec 17, 2014 at 04:28:23PM +0000, Linus Torvalds wrote:
>> On Wed, Dec 17, 2014 at 2:08 AM, Will Deacon <will.deacon@arm.com> wrote:
>> So why not just this trivial patch, to make the logic be the same it
>> used to be (just using "end > 0" instead of the old "need_flush")?
>
> Looks fine to me... Dave?
First of all, this is quite observable when testing single-threaded on a
desktop. This is a mildly crusty Sandybridge CPU from 2011. I made 3
runs with a single thread: ./brk1_processes -s 30 -t 1
fb7332a9fed : 4323385
fb7332a9fed^: 4503736
fb7332a9fed+Linus's fix: 4516761
These things are also a little bit noisy, so we're well within the
margin of error with Linus's fix.
This also holds up on the large system.
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave@sr71.net>
To: Will Deacon <will.deacon@arm.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Peter Zijlstra <peterz@infradead.org>,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
Michal Simek <monstr@monstr.eu>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: post-3.18 performance regression in TLB flushing code
Date: Wed, 17 Dec 2014 10:52:02 -0800 [thread overview]
Message-ID: <5491D0D2.5070103@sr71.net> (raw)
In-Reply-To: <20141217165310.GJ870@arm.com>
On 12/17/2014 08:53 AM, Will Deacon wrote:
> On Wed, Dec 17, 2014 at 04:28:23PM +0000, Linus Torvalds wrote:
>> On Wed, Dec 17, 2014 at 2:08 AM, Will Deacon <will.deacon@arm.com> wrote:
>> So why not just this trivial patch, to make the logic be the same it
>> used to be (just using "end > 0" instead of the old "need_flush")?
>
> Looks fine to me... Dave?
First of all, this is quite observable when testing single-threaded on a
desktop. This is a mildly crusty Sandybridge CPU from 2011. I made 3
runs with a single thread: ./brk1_processes -s 30 -t 1
fb7332a9fed : 4323385
fb7332a9fed^: 4503736
fb7332a9fed+Linus's fix: 4516761
These things are also a little bit noisy, so we're well within the
margin of error with Linus's fix.
This also holds up on the large system.
next prev parent reply other threads:[~2014-12-17 18:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-16 21:36 post-3.18 performance regression in TLB flushing code Dave Hansen
2014-12-17 10:08 ` Will Deacon
2014-12-17 10:08 ` Will Deacon
2014-12-17 16:28 ` Linus Torvalds
2014-12-17 16:53 ` Will Deacon
2014-12-17 16:53 ` Will Deacon
2014-12-17 18:52 ` Dave Hansen [this message]
2014-12-17 18:52 ` Dave Hansen
2014-12-17 19:58 ` Linus Torvalds
2014-12-17 19:58 ` Linus Torvalds
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