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[193.206.67.163]) by smtp.gmail.com with ESMTPSA id z1sm11828361wrv.90.2019.07.01.10.52.25 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 01 Jul 2019 10:52:26 -0700 (PDT) Message-ID: <3e7662d1391346dd11a903e66e7a8936ca83dba9.camel@unipv.it> Subject: Re: Slow I/O on USB media From: Andrea Vai To: Alan Stern Cc: Greg KH , linux-usb@vger.kernel.org Date: Mon, 01 Jul 2019 19:52:22 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Il giorno lun, 17/06/2019 alle 13.28 -0400, Alan Stern ha scritto: > On Mon, 17 Jun 2019, Andrea Vai wrote: > > > Il giorno lun, 17/06/2019 alle 12.14 -0400, Alan Stern ha scritto: > > > On Mon, 17 Jun 2019, Andrea Vai wrote: > > > > > > > [...] > > > > > > > > That happened ALL times, so I never encountered a kernel that > made > > > me > > > > say "git bisect good". > > > > > > Really? That strongly suggests that the 4.20 kernel also should > > > have > > > been marked bad. Did you really test it exactly the same way as > all > > > the others? That is, did you go through the entire procedure > > > starting > > > with "git checkout v4.20", then running the build script, then > the > > > reboot and "uname -a", and then the test script? > > > > well, honestly, no, because (sigh) I didn't know the "git > checkout" > > command, sorry. I started with building 4.20 from the source > > downloaded with > > > > wget > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/snapshot/linux-4.20.tar.gz > > > > , then said "git bisect good v4.20". > > > > Is this different from "git checkout v4.20"? I hope it is, so we > have > > found the mistake I have done. > > In theory the results should be exactly the same. But it doesn't > hurt > to check. > > > > Compare the mainstream 4.20 kernel with the Fedora 4.20.13 > kernel. > > > Also, maybe compare the mainstream 4.20.13 with Fedora's > 4.20.13. > > > > Sorry, what do you mean here by "compare"? And what is the > > "mainstream"? If the mainstream is the one I got with wget, and if > > "compare" means "see if they behave differently", so I have > already > > done it and they are both "good". > > I was trying to point out that there may be a significant difference > between 4.20 and 4.20.13. But if you say 4.20 behaves well, this > doesn't matter. > > At any rate, you are some commits you could try (beginning with > "git > checkout " and then running your scripts): > > c76cd634eb5b > b1669432b355 > 507413a5f88a > a52fb43a5faa > 38fabca18fc4 > fc2fd5f0f1aa > > These are all between 4.20 and 5.0-rc1. Hi, these were all "good". Then I ran another bisect (the sixth (!), more carefully, starting from git bisect good c76cd634eb5b git bisect bad 241e39004581 ), and it seems to give some consistent result. I found that: f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6 is the first bad commit commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6 Author: Jens Axboe Date: Thu Nov 1 16:36:27 2018 -0600 scsi: kill off the legacy IO path This removes the legacy (non-mq) IO path for SCSI. Cc: linux-scsi@vger.kernel.org Acked-by: Himanshu Madhani Reviewed-by: Hannes Reinecke Tested-by: Ming Lei Reviewed-by: Omar Sandoval Acked-by: Martin K. Petersen Signed-off-by: Jens Axboe :040000 040000 312373927bae1c6fd1da40ded2c12dfa5e4de71c 4eccbd2c84bf83cb2eb72a81514d59ebf12866b7 M Documentation :040000 040000 98de24b4fe20b82095f53f56c9193c5537d70ed0 8e2092780100205ae1c3723a598a89794a50677f M drivers :040000 040000 fbc10c84d3eb6b7933598018319f96767ee3a0f3 2523940c2819e8adb32758f5093e477da481ca65 M include I reverted it and the test succeeded. Then I made a double check: "git clone" again; git checkout 3a7ea2c483a53fc89e336f69c6ee1d7defe00811 (the last good), and the test succeded. Then git checkout f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6 (the first bad) and the test failed; then reverted it and the test succeded again. Does it make sense? Thanks, Andrea