linux-ext4 - Re: [Regression] ext4: changes to mb_optimize

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: <b8a5e43a-4d1e-aede-e0f7-f731fd8acf1d@i2se.com>
Date:   Tue, 16 Aug 2022 22:45:48 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org, Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>,
        Theodore Ts'o <tytso@....edu>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        linux-fsdevel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Geetika.Moolchandani1@....com, regressions@...ts.linux.dev,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [Regression] ext4: changes to mb_optimize_scan cause issues on
 Raspberry Pi

Hi Jan,

Am 16.08.22 um 11:34 schrieb Jan Kara:
> Hi Stefan!
> So this is interesting. We can see the card is 100% busy. The IO submitted
> to the card is formed by small requests - 18-38 KB per request - and each
> request takes 0.3-0.5s to complete. So the resulting throughput is horrible
> - only tens of KB/s. Also we can see there are many IOs queued for the
> device in parallel (aqu-sz columnt). This does not look like load I would
> expect to be generated by download of a large file from the web.
>
> You have mentioned in previous emails that with dd(1) you can do couple
> MB/s writing to this card which is far more than these tens of KB/s. So the
> file download must be doing something which really destroys the IO pattern
> (and with mb_optimize_scan=0 ext4 happened to be better dealing with it and
> generating better IO pattern). Can you perhaps strace the process doing the
> download (or perhaps strace -f the whole rpi-update process) so that we can
> see how does the load generated on the filesystem look like? Thanks!

i didn't create the strace yet, but i looked at the source of 
rpi-update. At the end the download phase is a curl call to download a 
tar archive and pipe it directly to tar.

You can find the content list of the tar file here:

https://raw.githubusercontent.com/lategoodbye/mb_optimize_scan_regress/main/rpi-firmware-tar-content-list.txt

Best regards

>
> 								Honza