________________________________________ From: Bart Van Assche [Bart.VanAssche@xxxxxxx] Sent: Tuesday, August 29, 2017 3:25 PM To: hch@xxxxxxxxxxxxx; Viswas G; Gerry Morong; Mahesh Rajashekhara; POSWALD@xxxxxxxx; Scott Benesh; Don Brace; Bader Ali - Saleh; Kevin Barnett; joseph.szczypek@xxxxxxx; Scott Teel; jejb@xxxxxxxxxxxxxxxxxx; Justin Lindley; John Hall Cc: linux-scsi@xxxxxxxxxxxxxxx Subject: Re: [PATCH] sd: preserve sysfs updates to max_sectors_kb EXTERNAL EMAIL On Tue, 2017-08-29 at 19:41 +0000, Don Brace wrote: > BLKRRPART ends up in the sd driver function sd_revalidate_disk, which resets > q->limits.max_sectors = min(rw_max, queue_max_hw_sectors(q)); > back to the value from VPD page 0xb0. > > When you cat out max_sectors_kb, it obtains it's valuse from q->limits.max_sectors > > Adding a udev rule... Will there be a delay between the watch rule and the new rule? Hello Don, In your original e-mail you wrote that max_sectors_kb was tuned because of performance reasons. So does it really matter that for a very short time max_sectors_kb does not have the optimal value? > One more point, what will I change the value back to? The watch rule > changed it and I do not have the original value. To the value you want to set max_sectors_kb to. Bart. Users do set max_sectors_kb for performance reasons. They can increase performance by setting max_sectors_kb to different values depending on their I/O needs. And, if they set the value, and sd_revalidate_disk changes this value, there is no history of what they set the value to. Thanks, Don Brace Microsemi Corp.
