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Date: Tue, 26 Jul 2022 17:54:46 +0200 From: Stefan Wahren <stefan.wahren@...e.com> To: Ojaswin Mujoo <ojaswin@...ux.ibm.com> Cc: linux-ext4@...r.kernel.org, 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 Subject: Re: [Regression] ext4: changes to mb_optimize_scan cause issues on Raspberry Pi Hi Ojaswin, Am 26.07.22 um 08:43 schrieb Ojaswin Mujoo: > On Mon, Jul 25, 2022 at 09:09:32PM +0200, Stefan Wahren wrote: >> Hi Ojaswin, >> >> Am 25.07.22 um 17:07 schrieb Ojaswin Mujoo: >>> On Mon, Jul 18, 2022 at 03:29:47PM +0200, Stefan Wahren wrote: >>>> Hi, >>>> >>>> i noticed that since Linux 5.18 (Linux 5.19-rc6 is still affected) i'm >>>> unable to run "rpi-update" without massive performance regression on my >>>> Raspberry Pi 4 (multi_v7_defconfig + CONFIG_ARM_LPAE). Using Linux 5.17 this >>>> tool successfully downloads the latest firmware (> 100 MB) on my development >>>> micro SD card (Kingston 16 GB Industrial) with a ext4 filesystem within ~ 1 >>>> min. The same scenario on Linux 5.18 shows the following symptoms: >>>> >>>> - download takes endlessly much time and leads to an abort by userspace in >>>> most cases because of the poor performance >>>> - massive system load during download even after download has been aborted >>>> (heartbeat LED goes wild) >>>> - whole system becomes nearly unresponsive >>>> - system load goes back to normal after > 10 min >>>> - dmesg doesn't show anything suspicious >>>> >>>> I was able to bisect this issue: >>>> >>>> ff042f4a9b050895a42cae893cc01fa2ca81b95c good >>>> 4b0986a3613c92f4ec1bdc7f60ec66fea135991f bad >>>> 25fd2d41b505d0640bdfe67aa77c549de2d3c18a bad >>>> b4bc93bd76d4da32600795cd323c971f00a2e788 bad >>>> 3fe2f7446f1e029b220f7f650df6d138f91651f2 bad >>>> b080cee72ef355669cbc52ff55dc513d37433600 good >>>> ad9c6ee642a61adae93dfa35582b5af16dc5173a good >>>> 9b03992f0c88baef524842e411fbdc147780dd5d bad >>>> aab4ed5816acc0af8cce2680880419cd64982b1d good >>>> 14705fda8f6273501930dfe1d679ad4bec209f52 good >>>> 5c93e8ecd5bd3bfdee013b6da0850357eb6ca4d8 good >>>> 8cb5a30372ef5cf2b1d258fce1711d80f834740a bad >>>> 077d0c2c78df6f7260cdd015a991327efa44d8ad bad >>>> cc5095747edfb054ca2068d01af20be3fcc3634f good >>>> 27b38686a3bb601db48901dbc4e2fc5d77ffa2c1 good >>>> >>>> commit 077d0c2c78df6f7260cdd015a991327efa44d8ad >>>> Author: Ojaswin Mujoo <ojaswin@...ux.ibm.com> >>>> Date: Tue Mar 8 15:22:01 2022 +0530 >>>> >>>> ext4: make mb_optimize_scan performance mount option work with extents >>>> >>>> If i revert this commit with Linux 5.19-rc6 the performance regression >>>> disappears. >>>> >>>> Please ask if you need more information. >>> Hi Stefan, >>> >>> Apologies, I had missed this email initially. So this particular patch >>> simply changed a typo in an if condition which was preventing the >>> mb_optimize_scan option to be enabled correctly (This feature was >>> introduced in the following commit [1]). I think with the >>> mb_optimize_scan now working, it is somehow causing the firmware >>> download/update to take a longer time. >>> >>> I'll try to investigate this and get back with my findings. >> thanks. I wasn't able to reproduce this heavy load symptoms with every SD >> card. Maybe this depends on the write performance of the SD card to trigger >> the situation (used command to measure write performance: dd if=/dev/zero >> of=/boot/test bs=1M count=30 oflag=dsync,direct ). >> >> I tested a Kingston consumer 32 GB which had nearly constant write >> performance of 13 MB/s and didn't had the heavy load symptoms. The firmware >> update was done in a few seconds, so hard to say that at least the >> performance regression is reproducible. >> >> I also tested 2x Kingston industrial 16 GB which had a floating write >> performance between 5 and 10 MB/s (wear leveling?) and both had the heavy >> load symptoms. >> >> All SD cards has been detected as ultra high speed DDR50 by the emmc2 >> interface. >> >> Best regards >> >>> Regard, >>> Ojaswin >>> >>> [1] >>> commit 196e402adf2e4cd66f101923409f1970ec5f1af3 >>> From: Harshad Shirwadkar <harshadshirwadkar@...il.com> >>> Date: Thu, 1 Apr 2021 10:21:27 -0700 >>> >>> ext4: improve cr 0 / cr 1 group scanning >>> >>>> Regards >>>> > Thanks for the info Stefan, I'm still trying to reproduce the issue but > it's slightly challenging since I don't have my RPi handy at the moment. > > In the meantime, would you please try out the mb_optmize_scan=0 command > line options to see if that helps bypass the issue. This will help > confirm if the issue lies in mb_optmize_scan itself or if its something > else. > I run the firmware update 5 times with mb_optimize_scan=0 on my Raspberry Pi 4 and the industrial SD card and everytime the update worked. > > Regards, > Ojaswin
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