linux-kernel - AW: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6

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Date:   Wed, 27 Nov 2019 08:14:43 +0000
From:   "Schmid, Carsten" <Carsten_Schmid@...tor.com>
To:     Finn Thain <fthain@...egraphics.com.au>,
        Andrea Vai <andrea.vai@...pv.it>
CC:     Ming Lei <ming.lei@...hat.com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Alan Stern <stern@...land.harvard.edu>,
        Jens Axboe <axboe@...nel.dk>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        USB list <linux-usb@...r.kernel.org>,
        SCSI development list <linux-scsi@...r.kernel.org>,
        Himanshu Madhani <himanshu.madhani@...ium.com>,
        Hannes Reinecke <hare@...e.com>,
        Omar Sandoval <osandov@...com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Hans Holmberg <Hans.Holmberg@....com>,
        Kernel development list <linux-kernel@...r.kernel.org>
Subject: AW: Slow I/O on USB media after commit
 f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6

> 
> > Then I started another set of 100 trials and let them run tonight, and
> > the first 10 trials were around 1000s, then gradually decreased to
> > ~300s, and finally settled around 200s with some trials below 70-80s.
> > This to say, times are extremely variable and for the first time I
> > noticed a sort of "performance increase" with time.
> >
> 
> The sheer volume of testing (probably some terabytes by now) would
> exercise the wear leveling algorithm in the FTL.
> 
But with "old kernel" the copy operation still is "fast", as far as i understood.
If FTL (e.g. wear leveling) would slow down, we would see that also in
the old kernel, right?

Andrea, can you confirm that the same device used with the old fast
kernel is still fast today?

BR
Carsten