Alt-L locks the display but does it also slow down running programs?

The subject is the question. I ask because I sometimes
start a (long) full backup to an external drive and walk
away. After a while, Windows will lock the session so I
have to sign in again later. When I do, I can't help but
think that the backup job has been running more slowly
than before. Am I imagining that?

Jason wrote:
The subject is the question. I ask because I sometimes
start a (long) full backup to an external drive and walk
away. After a while, Windows will lock the session so I
have to sign in again later. When I do, I can't help but
think that the backup job has been running more slowly
than before. Am I imagining that?

Perfmon.msc has an item on the left, to log to file.

This allows you to record performance counters versus time.
For example "Disk Read Bytes/sec" and "Disk Write Bytes/sec"
are counters you can log (or plot). Later, you can plot the
CSV data in Excel or LibreOffice Calc.

What you'd do, is two identical test runs. One where
you did the backup, and kept the screen open. Then,
a second backup run where the screen was allow to blank
or whatever. You should compare full traces (i.e. take
the log file full of CSV data and plot in Excel). By comparing
full traces, that accounts for natural variations in transfer
rate.

A simple stop-watch test would do as much, to answer the
question. Do two backups. If the completion time is logged,
use that, or use a stopwatch. Do your second run and apply
your test conditions, and see if the stopwatch time is different.
That method won't provide details (how much the performance
dropped), but it's easier to set up.

*******

For some benchmark tests, you need to flush the System Read Cache,
to make the test setup "fair" between runs. If the backup is
big enough, it will naturally flush the read cache. On some
of the review web sites, the easiest way for them to make
identical runs, is to reboot before each run. On Windows 10,
you'd unplug the network cable, to prevent any "maintenance"
activity in Win10, from fouling your test results. Win10 gets
a lot quieter, with the cable unplugged.

Paul

Jason wrote:

The subject is the question. I ask because I sometimes start a (long)
full backup to an external drive and walk away. After a while,
Windows will lock the session so I have to sign in again later. When
I do, I can't help but think that the backup job has been running
more slowly than before. Am I imagining that?

Yep, your imagination. Even if the backup program was issuing output to
the video device, doesn't matter if it isn't displayed.

However, is "lock" actually the screen going blank because the computer
went into *sleep* mode? If so, yep, then everything runs slower or even
halts. The computer is supposed to be sleeping. You would think that
running a backup job would keep the computer from sleeping. Well,
perhaps for the CPU but not necessarily for the hard disk, especially if
it is one of those "green" drives that spins down and goes into its own
sleep mode. I've need backup jobs that have to spend a LONG time
compressing a part of a file, especially if the user elects to use the
highest compression the backup program offers (which often provides
little reduction in backup file size over normal compression level).
The CPU is busy crunching away but the green disk sees no activity so it
spins down. Then it has to power up and spin up. Repeat ad nauseum.
If the green drive doesn't wake up fast enough, the backup program might
assume the destination drive is unresponsive and abort the backup job.

Have you measure how long a backup takes without the computer locking up
(screen saver, standby mode, or whatever causes the lock) and then
measured a following duplicate backup (with little change to the drive's
contents) with the locking enabled?

In article , says...
Have you measure how long a backup takes without the computer locking up
(screen saver, standby mode, or whatever causes the lock) and then
measured a following duplicate backup (with little change to the drive's
contents) with the locking enabled?


I haven't yet, but you and Paul both suggested it so I'll give it a try.
The machine is not sleeping - it would be obvious if it were. So it
probably is my imagination after all. :-)

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