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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
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