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.
next prev parent reply other threads:[~2022-12-01 21:22 UTC|newest]
Thread overview: 19+ 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
2022-10-19 2:05 ` Huang, Ying
2022-10-20 4:23 ` Nathan Chancellor
2022-10-20 5:07 ` Huang, Ying
2022-10-20 15:28 ` Rik van Riel
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
2022-11-29 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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