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From: Andrew Morton <akpm@linux-foundation.org>
To: Rik van Riel <riel@surriel.com>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>,
	Yang Shi <shy828301@gmail.com>,
	"Huang, Ying" <ying.huang@intel.com>,
	kernel test robot <yujie.liu@intel.com>,
	lkp@lists.01.org, lkp@intel.com,
	Matthew Wilcox <willy@infradead.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	feng.tang@intel.com, zhengjun.xing@linux.intel.com,
	fengwei.yin@intel.com, Nathan Chancellor <nathan@kernel.org>
Subject: Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression
Date: Thu, 1 Dec 2022 13:22:37 -0800	[thread overview]
Message-ID: <20221201132237.c55c4bd07ba44463b146882e@linux-foundation.org> (raw)
In-Reply-To: <07adee081a70c2b4b44d9bf93a0ad3142e091086.camel@surriel.com>

On Thu, 01 Dec 2022 15:29:41 -0500 Rik van Riel <riel@surriel.com> wrote:

> On Thu, 2022-12-01 at 19:33 +0100, Thorsten Leemhuis wrote:
> > Hi, this is your Linux kernel regression tracker.
> > 
> > On 28.11.22 07:40, Nathan Chancellor wrote:
> > > Hi Rik,
> > 
> > I wonder what we should do about below performance regression. Is
> > reverting the culprit now and reapplying it later together with a fix
> > a
> > viable option? Or was anything done/is anybody doing something
> > already
> > to address the problem and I just missed it?
> 
> The changeset in question speeds up kernel compiles with
> GCC, as well as the runtime speed of other programs, due
> to being able to use THPs more. However, it slows down kernel
> compiles with clang, due to ... something clang does.
> 
> I have not figured out what that something is yet.
> 
> I don't know if I have the wrong version of clang here,
> but I have not seen any smoking gun at all when tracing
> clang system calls. I see predominantly small mmap and
> unmap calls, and nothing that even triggers 2MB alignment.

2.8% speedup for gcc is nice.  Massive slowdown in the malloc banchmark
and in LLVM/clang is very bad - we don't know what other userspace will
be so affected.

So I think we revert until this is fully understood.



  reply	other threads:[~2022-12-01 21:22 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-18  8:44 [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression kernel test robot
2022-10-18  8:44 ` kernel test robot
2022-10-19  2:05 ` Huang, Ying
2022-10-19  2:05   ` Huang, Ying
2022-10-20  4:23   ` Nathan Chancellor
2022-10-20  4:23     ` Nathan Chancellor
2022-10-20  5:07     ` Huang, Ying
2022-10-20  5:07       ` Huang, Ying
2022-10-20 15:28       ` Rik van Riel
2022-10-20 15:28         ` Rik van Riel
2022-10-20 17:16         ` Nathan Chancellor
2022-10-20 17:16           ` Nathan Chancellor
2022-11-28  6:40           ` Nathan Chancellor
2022-12-01 18:33             ` Thorsten Leemhuis
2022-12-01 20:29               ` Rik van Riel
2022-12-01 21:22                 ` Andrew Morton [this message]
2022-12-01 21:44                   ` Yang Shi
2022-12-02  8:46                   ` Thorsten Leemhuis
2022-12-02 18:44                     ` Andrew Morton
2022-12-02 19:37                       ` Thorsten Leemhuis
2022-12-01 21:35                 ` Nathan Chancellor
2022-12-16 11:48                 ` Yin, Fengwei
2022-10-20 16:40       ` Yujie Liu
2022-10-20 16:40         ` Yujie Liu
2022-11-29  8:59     ` [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression #forregzbot Thorsten Leemhuis
2022-12-02  6:43       ` Thorsten Leemhuis

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