linux-kernel - Re: [REGRESSION]: mmap performance regression starting with k-6.1

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZV7eHE2Fxb75oRpG@archie.me>
Date:   Thu, 23 Nov 2023 12:07:40 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     Chun Ng <chunn@...dia.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Linux Regressions <regressions@...ts.linux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Ankita Garg <ankitag@...dia.com>
Subject: Re: [REGRESSION]: mmap performance regression starting with k-6.1

On Wed, Nov 22, 2023 at 08:03:19PM +0000, Chun Ng wrote:
> Hi,
> 
> Recently I observed there is performance regression on system call mmap(..). I tried both vanilla kernels and Raspberry Pi kernels on a Raspberry Pi 4 box and the results are pretty consistent among them.
> 
> Bisection showed that the regression starts from k-6.1, and the latest vanilla k-6.7 is still showing the same regression.
> 
> The test program calls mmap/munmap for a 4K page with MAP_ANON and MAP_PRIVATE flags, and ftrace is used to measure the time spent on the do_mmap(..) call.  Measured time of a sample run with different vanilla kernel versions are:
> k-5.10 and k-6.0: ~157us
> k-6.1: ~194us
> k-6.7: ~214us
> Results are pretty consistent across multiple runs with a small percentage variance.  Ftrace shows that latency of mmap_region(...) has increased since k-6.1.  An application that makes frequent mmap(..) calls the accumulated extra latency is very noticeable. 
> 
> Please find the ftrace results and kernel config files in this folder:
> https://drive.google.com/drive/folders/1qy8YTBqxu8Gdbs7IigYbSd4FXldId5sd?usp=drive_link
> 
> The test program can be found in here:
> https://drive.google.com/file/d/1tG6_BbQMCHwfKebvAIAg_xqbM_lpPcuM/view?usp=sharing
> 
> Info on the testing environment:
> cpufreq_governor: performance
> Test machine: Raspberry Pi 4, 8GB DDR
> SCHED_FIFO with priority 99 for running the test program
> 
> Vanilla kernels are not tainted. However on k-6.0 and k-6.7, I have to patch the drivers/clk/bcm/clk-raspberrypi.c file with the version in Raspberry Pi kernel tree for the CPU frequency governor to work.
> 

The next step is to find the commit that introduces your regression with
`git bisect`. If you haven't done so, see
Documentation/admin-guide/bug-bisect.rst for instructions.

Anyway, I'm adding this regression to regzbot:

#regzbot ^introduced: v6.0..v6.1

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)