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Re^4: Windows 7 Remove Tabs Out of Memory

by Anonymous Monk
on Aug 01, 2012 at 13:09 UTC ( #984786=note: print w/ replies, xml ) Need Help??


in reply to Re^3: Windows 7 Remove Tabs Out of Memory
in thread Windows 7 Remove Tabs Out of Memory

Actually no. That forces the OS to keep the disk head moving back and forth between source(*) and destination.

It doesn't "force", actually. But as I stated in my post, I have yet to see an OS that could handle such a simple single-threaded situation intelligently enough. (That is, delay writing until file is closed or otherwise absolutely necessary.)

BTW, there is something odd with your numbers. The Perl timestamps only give a delta of slightly less than six seconds (~83 MB/s average => reading 228 MB/s, writing 152 MB/s), but your console says almost 22 seconds (which would put the performance at around 23 MB/s)


Comment on Re^4: Windows 7 Remove Tabs Out of Memory
Re^5: Windows 7 Remove Tabs Out of Memory
by BrowserUk (Pope) on Aug 01, 2012 at 13:43 UTC
    BTW, there is something odd with your numbers. The Perl timestamps only give a delta of slightly less than six seconds (~83 MB/s average => reading 228 MB/s, writing 152 MB/s), but your console says almost 22 seconds (which would put the performance at around 23 MB/s)

    The difference between the timestamps and the prompt timing is because the prompt had been sat there for a few seconds before (and during) my typing the command.

    Here are two sets of prompts, the first shows the prompt had been sat idle for a while before I entered the command. The second run, initiated using command retrieval whilst the first run was in progress executes immediately the first is complete and the delta then reflects the timestamps output by the program:

    [14:19:53.80] C:\test>984648-3.pl 500MB.csv junk.txt 1343827530.71078 1343827532.87958 1343827533.36184 ## Delta here several minute +s 1343827536.56099 [14:25:36.61] C:\test>984648-3.pl 500MB.csv junk.txt 1343827536.68696 1343827538.87822 1343827539.3639 ## delta here a gnat's under + 7 seconds! 1343827543.53711 [14:25:43.58] C:\test>

    And as far as IO throughput, here's a snapshot of the process performance dialog from Process Explorer after the process finished.

    Each vertical gridline represents 3 seconds.

    The cyan is the read, and the throughput is shown in the small popup. 120.2MB/0.5 seconds. 500/120.2/2 = 2.0798668885191347753743760399334 seconds to read,

    The purple is the write and the throughput is shown on the gauge at the left. 90.4MB/0.5 seconds. 500/90.4/2 = 2.7654867256637168141592920353982 seconds to write.

    Slightly optimistic figures, but the total throughput is the area, and if you look closely, you'll see the top of the graphs aren't straight and the leading and trailing edges aren't vertical.


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