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Mid 2011 Macbook Air Painfully slow.

Mid 2011 Macbook Air Painfully slow.


Hey everyone. I am writing about my 13 inch Mid 2011 Macbook Air.


Recently it has been extremely slow and on occasion has not started up.


I have reset the PRAM and SMC already, yet it is still very slow. I have a couple theories about what might have caused it, are they plausible?


Theory 1: It’s a software problem. I tried to upgrade to 10.8.2 but halfway through the upgrade the computer restarted and somehow I was still on 10.8.1. For fear of a big issue happening I didn’t try to upgrade again. Perhaps it is a flaw in Apple’s software update?


The important thing to note about this update is that I tried to install 10.8.2 around a month or two weeks BEFORE I started having problems. So if these issues were due to 10.8.2’s failed update then it certainly was a delayed reaction.


I would of course like to update to 10.8.2 BUT as my computer is acting EXTREMELY slow and having trouble turning on occasionally I am worried the software update will completely brick the machine. Is that possible? Should I actually finish through with the software update?


Theory 2: It was an electricity problem.


The computer died when I was sitting at a café plugged into their wall sockets. A few days later when I came back to the same spot with my old macbook which is now being used in lieu of the Air it suddenly turned black for a little while. Sensing it might be an electricity surge or something with their system I unplugged the cable. I am not sure if that was paranoia though.


Can an electricity surge or a bad outlet fry a computer? Can it fry the ram so the computer is extremely slow? Does that theory hold any water?



Thanks for your help diagnosing this problem.


All the best.

MacBook Air, OS X Mountain Lion (10.8.1)

Posted on Oct 2, 2012 11:12 AM

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Question marked as Best reply

Posted on Oct 2, 2012 11:21 AM

Shut down your MBA and restart while holding the D key. This should start Apple Hardware Test. Run the default tests. If everything passes "no problems found" then run the extended tests, which might take 45 minutes. Report anything other than "no problems found".


I have no reason to believe updating OS X would be cause for concern, and might fix the problem. Try downloading and installing the update again.

… Can an electricity surge or a bad outlet fry a computer? Can it fry the ram so the computer is extremely slow? Does that theory hold any water?


Anything is possible but all Apple portables are fairly isolated from power quality problems like you suspect. Any surge would have to pass through the charger as well as the battery, both of which absorb a certain amount of energy before it is capable of causing more damage.

13 replies
Question marked as Best reply

Oct 2, 2012 11:21 AM in response to ZXA

Shut down your MBA and restart while holding the D key. This should start Apple Hardware Test. Run the default tests. If everything passes "no problems found" then run the extended tests, which might take 45 minutes. Report anything other than "no problems found".


I have no reason to believe updating OS X would be cause for concern, and might fix the problem. Try downloading and installing the update again.

… Can an electricity surge or a bad outlet fry a computer? Can it fry the ram so the computer is extremely slow? Does that theory hold any water?


Anything is possible but all Apple portables are fairly isolated from power quality problems like you suspect. Any surge would have to pass through the charger as well as the battery, both of which absorb a certain amount of energy before it is capable of causing more damage.

Oct 2, 2012 12:13 PM in response to ZXA

First, back up all data immediately, as your boot drive might be failing.


Take these steps when you notice the problem.


Step 1


Launch the Activity Monitor application in any of the following ways:


☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)


☞ In the Finder, select Go Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.


☞ Open LaunchPad. Click Utilities, then Activity Monitor in the icon grid.


Select the CPU tab of the Activity Monitor window.


Select All Processes from the menu in the toolbar, if not already selected.


Click the heading of the % CPU column in the process table to sort the entries by CPU usage. You may have to click it twice to get the highest value at the top. What is it, and what is the process? Also post the values for % User, % System, and % Idle at the bottom of the window.


Select the System Memory tab. What values are shown in the bottom part of the window for Page outs and Swap used?


Next, select the Disk Activity tab. Post the approximate values shown for Reads in/sec and Writes out/sec (not Reads in and Writes out.)


Step 2


You must be logged in as an administrator to carry out this step.


Launch the Console application in the same way as above. Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left.


Post the 50 or so most recent messages in the log — the text, please, not a screenshot.


When posting a log extract, be selective. Don't post more than is requested.

Please do not indiscriminately dump thousands of lines from the log into a message.

Important: Some personal information, such as your name, may appear in the log. Edit it out before posting.

Oct 2, 2012 12:38 PM in response to ZXA

Thanks John. I will do the Hardware damage check as soon as possible. I am currently backing up my whole computer (slowly but surely....) just in case it won't turn on again. I will also look into the software update after the backup. I'll reply again later today or tomorrow (Whenver the backup is complete) I really appreciate your extremely fast response.

Oct 2, 2012 1:02 PM in response to Linc Davis

Hey Linc,


Thanks for your response. We might be on to something here, because in Activity Monitor it shows a "kernel_task" taking up 322% of the CPU. On another thread someone said booting in safe mode solved this problem (but a software update did not).


User is 12%


System 78%


Idle is 10%


Page outs and swap are both 0.


Read in is: was stuck at 0 for a long time, then was at 4, then back to 0, then now it's at 400. Very erratic. (back to zero now).

Read out is: 0 most of the time, when it went to 400 it did jump up near 400 as well.


This is the post of around 50 logs:


User uploaded file


10/2/12 3:20:17.055 PM loginwindow[53]: CGSGetWindowTags: Invalid window 0xffffffff

10/2/12 3:20:17.055 PM loginwindow[53]: find_shared_window: WID -1

10/2/12 3:20:17.056 PM loginwindow[53]: CGSSetWindowTags: Invalid window 0xffffffff

10/2/12 3:20:17.179 PM loginwindow[53]: ERROR | -[LWBuiltInScreenLockAuthLion preLoad] | guestEnabled is true, but guest mode is not set to a usable value

10/2/12 3:20:18.634 PM WindowServer[75]: Created shield window 0xa2 for display 0x042737c0

10/2/12 3:20:18.634 PM WindowServer[75]: device_generate_desktop_screenshot: authw 0x7feb3c888290(2000), shield 0x7feb3ead4d70(2001)

10/2/12 3:20:20.232 PM WindowServer[75]: device_generate_lock_screen_screenshot: authw 0x7feb3c888290(2000), shield 0x7feb3ead4d70(2001)

10/2/12 3:30:15.085 PM WindowServer[75]: handle_will_sleep_auth_and_shield_windows: releasing authw 0x7feb3c888290(2000), shield 0x7feb3ead4d70(2001), lock state 3

10/2/12 3:30:15.115 PM WindowServer[75]: handle_will_sleep_auth_and_shield_windows: err 0x0

10/2/12 3:39:37.000 PM kernel[0]: MacAuthEvent en0 Auth result for: 68:7f:74:3a:72:7e MAC AUTH succeeded

10/2/12 3:39:37.000 PM kernel[0]: wlEvent: en0 en0 Link UP virtIf = 0

10/2/12 3:39:37.000 PM kernel[0]: wl0: Roamed or switched channel, reason #8, bssid 68:7f:74:3a:72:7e

10/2/12 3:39:37.000 PM kernel[0]: en0: BSSID changed to 68:7f:74:3a:72:7e

10/2/12 3:39:37.000 PM kernel[0]: en0::IO80211Interface::postMessage bssid changed

10/2/12 3:39:38.000 PM kernel[0]: AirPort: RSN handshake complete on en0

10/2/12 3:39:54.000 PM kernel[0]: MacAuthEvent en0 Auth result for: 68:7f:74:3a:72:7e MAC AUTH succeeded

10/2/12 3:39:54.000 PM kernel[0]: wlEvent: en0 en0 Link UP virtIf = 0

10/2/12 3:39:54.000 PM kernel[0]: wl0: Roamed or switched channel, reason #8, bssid 68:7f:74:3a:72:7e

10/2/12 3:39:54.000 PM kernel[0]: en0: BSSID changed to 68:7f:74:3a:72:7e

10/2/12 3:39:54.000 PM kernel[0]: en0::IO80211Interface::postMessage bssid changed

10/2/12 3:39:55.000 PM kernel[0]: AirPort: RSN handshake complete on en0

10/2/12 3:44:55.850 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Activity Monitor" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:44:55.851 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Activity Monitor" after 1.11 seconds (server forcibly re-enabled them after 1.11 seconds)

10/2/12 3:46:24.835 PM Google Chrome Helper[1774]: Unsure about the internals of CFAllocator but going to patch them anyway. If there is a crash inside of CFAllocatorAllocate, please report it at http://crbug.com/117476 . If there is a crash and it is NOT inside of CFAllocatorAllocate, it is NOT RELATED. DO NOT REPORT IT THERE but rather FILE A NEW BUG.

10/2/12 3:46:31.000 PM Google Chrome Helper[1775]: Unsure about the internals of CFAllocator but going to patch them anyway. If there is a crash inside of CFAllocatorAllocate, please report it at http://crbug.com/117476 . If there is a crash and it is NOT inside of CFAllocatorAllocate, it is NOT RELATED. DO NOT REPORT IT THERE but rather FILE A NEW BUG.

10/2/12 3:46:39.971 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Activity Monitor" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:46:40.214 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Activity Monitor" after 1.31 seconds (server forcibly re-enabled them after 1.06 seconds)

10/2/12 3:46:43.295 PM Google Chrome Helper[1775]: CGSLookupServerRootPort: Failed to look up the port for "com.apple.windowserver.active" (1100)

10/2/12 3:46:46.053 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Activity Monitor" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:46:46.054 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Console" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:46:46.104 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Activity Monitor" after 1.06 seconds (server forcibly re-enabled them after 1.00 seconds)

10/2/12 3:46:46.106 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Console" after 1.06 seconds (server forcibly re-enabled them after 1.01 seconds)

10/2/12 3:46:47.874 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Activity Monitor" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:46:47.912 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Activity Monitor" after 1.04 seconds (server forcibly re-enabled them after 1.00 seconds)

10/2/12 3:46:59.793 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Activity Monitor" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:47:00.036 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Activity Monitor" after 1.34 seconds (server forcibly re-enabled them after 1.09 seconds)

10/2/12 3:47:39.896 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Activity Monitor" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:47:40.123 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Activity Monitor" after 1.28 seconds (server forcibly re-enabled them after 1.05 seconds)

10/2/12 3:47:54.605 PM Google Chrome Helper EH[1778]: Unsure about the internals of CFAllocator but going to patch them anyway. If there is a crash inside of CFAllocatorAllocate, please report it at http://crbug.com/117476 . If there is a crash and it is NOT inside of CFAllocatorAllocate, it is NOT RELATED. DO NOT REPORT IT THERE but rather FILE A NEW BUG.

10/2/12 3:48:01.403 PM Google Chrome Helper EH[1779]: Unsure about the internals of CFAllocator but going to patch them anyway. If there is a crash inside of CFAllocatorAllocate, please report it at http://crbug.com/117476 . If there is a crash and it is NOT inside of CFAllocatorAllocate, it is NOT RELATED. DO NOT REPORT IT THERE but rather FILE A NEW BUG.

10/2/12 3:56:56.185 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Console" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:56:56.626 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Console" after 1.44 seconds (server forcibly re-enabled them after 1.00 seconds)

10/2/12 3:56:57.820 PM WindowServer[75]: CGXDisableUpdate: UI updates were forcibly disabled by application "Console" for over 1.00 seconds. Server has re-enabled them.

10/2/12 3:56:58.373 PM WindowServer[75]: reenable_update_for_connection: UI updates were finally reenabled by application "Console" after 1.56 seconds (server forcibly re-enabled them after 1.01 seconds)



Thanks for your help--- I am sorry I've been so slow responding. Both my Air and this computer (due to age) are frightfully laggy.


I really appreciate this.

Oct 2, 2012 1:35 PM in response to ZXA

Please read this whole message before doing anything.


This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.


The purpose of this exercise is to determine whether the problem is caused by third-party system modifications that load automatically at startup or login. Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards. Boot in safe mode* and log in to the account with the problem. The instructions provided by Apple are as follows:


  1. Shut down your computer, wait 30 seconds, and then hold down the shift key while pressing the power button.
  2. When you see the gray Apple logo, release the shift key.
  3. If you are prompted to log in, type your password, and then hold down the shift key again as you click Log in.


*Note: If FileVault is enabled under OS X 10.7 or later, or if a firmware password is set, or if the boot volume is a software RAID, you can’t boot in safe mode.


Safe mode is much slower to boot than normal, and some things won’t work at all, including wireless networking on certain Macs.


The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.


Test while in safe mode. Same problem(s)?


After testing, reboot as usual (i.e., not in safe mode) and verify that you still have the problem. Post the results of the test.

Oct 5, 2012 1:14 PM in response to Linc Davis

Sorry I've been so slow--- been backing up everything. Which of course, is slow it itself.


Anyway, I'm in safe mode now and everything is much faster, although not perfect. I am not sure if that is due to safe modes inherent performance or a legacy result of my problems in unsafe mode (hehe).


For a little while "Windows Server" was near 110% of CPU, but it has since gone down to 5.6%. Kernel_task is also at about 1.8% although it does have 62 threads.


So it appears safe mode greatly improves my computers performance. What are the next steps based on this knowledge?

Oct 5, 2012 1:23 PM in response to ZXA

Please read this whole message before doing anything.

This procedure is a diagnostic test. It won’t solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.

Third-party system modifications are a common cause of usability problems. By a “system modification,” I mean software that affects the operation of other software — potentially for the worse. The following procedure will help identify which such modifications you've installed. Don’t be alarmed by the complexity of these instructions — they’re easy to carry out and won’t change anything on your Mac.


These steps are to be taken while booted in “normal” mode, not in safe mode. If you’re now running in safe mode, reboot as usual before continuing.


Below are instructions to enter some UNIX shell commands. The commands are harmless, but they must be entered exactly as given in order to work. If you have doubts about the safety of the procedure suggested here, search this site for other discussions in which it’s been followed without any report of ill effects.


Some of the commands will line-wrap or scroll in your browser, but each one is really just a single line, all of which must be selected. You can accomplish this easily by triple-clicking anywhere in the line. The whole line will highlight, and you can then either copy or drag it. The headings “Step 1” and so on are not part of the commands.


Note: If you have more than one user account, Step 2 must be taken as an administrator. Ordinarily that would be the user created automatically when you booted the system for the first time. The other steps should be taken as the user who has the problem, if different. Most personal Macs have only one user, and in that case this paragraph doesn’t apply.


Launch the Terminal application in any of the following ways:


☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)


☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.


☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.


When you launch Terminal, a text window will open with a line already in it, ending either in a dollar sign (“$”) or a percent sign (“%”). If you get the percent sign, enter “sh” and press return. You should then get a new line ending in a dollar sign.


Step 1


Copy or drag — do not type — the line below into the Terminal window, then press return:

kextstat -kl | awk '!/com\.apple/{printf "%s %s\n", $6, $7}'

Post the lines of output (if any) that appear below what you just entered (the text, please, not a screenshot.) You can omit the final line ending in “$”.


Step 2


Repeat with this line:

sudo launchctl list | sed 1d | awk '!/0x|com\.(apple|openssh|vix)|edu\.mit|org\.(amavis|apache|cups|isc|ntp|postfix|x)/{print $3}'

This time, you'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up. You don't need to post the warning.


Note: If you don’t have a login password, you’ll need to set one before taking this step. If that’s not possible, skip to the next step.


Step 3

launchctl list | sed 1d | awk '!/0x|com\.apple|edu\.mit|org\.(x|openbsd)/{print $3}'

Step 4

ls -1A /e*/mach* {,/}L*/{Ad,Compon,Ex,Fram,In,Keyb,La,Mail/Bu,P*P,Priv,Qu,Scripti,Servi,Spo,Sta}* L*/Fonts 2> /dev/null

Important: If you formerly synchronized with a MobileMe account, your me.com email address may appear in the output of the above command. If so, anonymize it before posting.


Step 5

osascript -e 'tell application "System Events" to get name of every login item' 2> /dev/null

Remember, steps 1-5 are all drag-and-drop or copy-and-paste, whichever you prefer — no typing, except your password. Also remember to post the output.


You can then quit Terminal.

Oct 8, 2012 4:36 PM in response to ZXA

ZXA,


I had the exact same problem. Kernel activity going up to more than 300% and everything else slowing down with the fan at full speed. I did the hardware tests and they showed no faults. As I was about to do a clean install, the MBA quieted down and everything is back to normal now. Whatever was making it go crazy has gone away. I have tried a lot of things before, safe boot, reset PRAM, reset SMC, but nothing worked. As it is now, the mystery is not solved.


Good luck on yours and hope the helpful Linc can provide some insight into the problem.


Cheers,

Harman

MBA 13 early 2012

Dec 26, 2012 10:32 AM in response to Linc Davis

Sorry I have taken so long to reply. Been very busy with work and I just didn't want to wade back into this issue at the time.


Now that I have the time I have undergone the tests, here are the results. Thank you very much for your help, Merry Christmas.



Works-MacBook-Air:~ work$ kextstat -kl | awk '!/com\.apple/{printf "%s %s\n", $6, $7}'


Works-MacBook-Air:~ work$ sudo launchctl list | sed 1d | awk '!/0x|com\.(apple|openssh|vix)|edu\.mit|org\.(amavis|apache|cups|isc|ntp|postfi x|x)/{print $3}'

WARNING: Improper use of the sudo command could lead to data loss

or the deletion of important system files. Please double-check your

typing when using sudo. Type "man sudo" for more information.

To proceed, enter your password, or type Ctrl-C to abort.

Password:

watcom.microsoft.office.licensing.helper

com.crashplan.engine

com.adobe.SwitchBoard

Works-MacBook-Air:~ work$

-bash: : command not found

Works-MacBook-Air:~ work$ launchctl list | sed 1d | awk '!/0x|com\.apple|edu\.mit|org\.(x|openbsd)/{print $3}'

com.adobe.CS5ServiceManager

com.google.keystone.user.agent

Works-MacBook-Air:~ work$ ls -1A /e*/mach* {,/}L*/{Ad,Compon,Ex,Fram,In,Keyb,La,Mail/Bu,P*P,Priv,Qu,Scripti,Servi,Spo,Sta} * L*/Fonts 2> /dev/null

/Library/Components:

/Library/Extensions:

/Library/Frameworks:

AEProfiling.framework

AERegistration.framework

Adobe AIR.framework

AudioMixEngine.framework

NyxAudioAnalysis.framework

PluginManager.framework

iTunesLibrary.framework

/Library/Input Methods:

/Library/Internet Plug-Ins:

AmazonMP3DownloaderPlugin.plugin

AmazonMP3DownloaderPlugin1017277.plugin

Flash Player.plugin

JavaAppletPlugin.plugin

Quartz Composer.webplugin

QuickTime Plugin.plugin

SharePointBrowserPlugin.plugin

SharePointWebKitPlugin.webplugin

flashplayer.xpt

nsIQTScriptablePlugin.xpt

/Library/Keyboard Layouts:

/Library/LaunchAgents:

com.adobe.AAM.Updater-1.0.plist

com.adobe.CS5ServiceManager.plist

/Library/LaunchDaemons:

com.adobe.SwitchBoard.plist

com.crashplan.engine.plist

com.microsoft.office.licensing.helper.plist

/Library/PreferencePanes:

Flash Player.prefPane

Growl.prefPane

/Library/PrivilegedHelperTools:

com.microsoft.office.licensing.helper

/Library/QuickLook:

iBooksAuthor.qlgenerator

iWork.qlgenerator

/Library/QuickTime:

AppleIntermediateCodec.component

AppleMPEG2Codec.component

/Library/ScriptingAdditions:

Adobe Unit Types.osax

/Library/Spotlight:

Microsoft Office.mdimporter

iBooksAuthor.mdimporter

iWork.mdimporter

/Library/StartupItems:

/etc/mach_init.d:

/etc/mach_init_per_login_session.d:

/etc/mach_init_per_user.d:

Library/Address Book Plug-Ins:

SkypeABDialer.bundle

SkypeABSMS.bundle

Library/Fonts:

BrannbollFet.ttf

BrannbollSmal.ttf

KnarfArtFont-Bold.otf

KnarfArtFont-Regular.otf

LAZYTOWN.ttf

Lead.ttf

OrnamentalVersals.ttf

OrnamentalVersals_Black.ttf

Perforama.otf

PermanentMarker.ttf

Perspective.ttf

PressureWash.ttf

REBOARD FONT.ttf

TEAMSPIR.TTF

Thirties Gold.ttf

Venus Furs 2.ttf

collegiateHeavyOutline Medium.ttf

hauptbahnhof.ttf

saytwo.ttf

teardrop by Blastto.ttf

vtks Rude Metal Shadow.ttf

Library/Frameworks:

SamsungKiesFoundation.framework

SamsungKiesSerialPort.framework

Library/Input Methods:

.localized

Library/Internet Plug-Ins:

Library/Keyboard Layouts:

Library/LaunchAgents:

com.apple.AddressBook.ScheduledSync.PHXCardDAVSource.F579FB92-3FA1-4FDC-ADEF-9F7 8BD6C0D4D.plist

com.apple.FolderActions.enabled.plist

com.apple.FolderActions.folders.plist

com.google.keystone.agent.plist

Library/PPS:

.mplayer

.pps

co.ppstream.Geometry.plist

co.ppstream.pps_area.plist

co.ppstream.pps_list.plist

co.ppstream.pps_login.plist

co.ppstream.pps_player.plist

co.ppstream.pps_update.plist

Library/PreferencePanes:

Library/Services:

Works-MacBook-Air:~ work$ osascript -e 'tell application "System Events" to get name of every login item' 2> /dev/null

iTunesHelper, Flux, CrashPlan menu bar, KiesViaWiFiAgent, Dropbox, fuspredownloader

Works-MacBook-Air:~ work$

Works-MacBook-Air:~ work$

Jan 9, 2013 2:43 PM in response to ZXA

The kernel is using excessive processor cycles. Below is a partial list of causes for this condition.

Thermal overload

This can be due to accumulation of dust, high ambient temperature, or to the malfunction of a cooling fan or temperature sensor. The kernel tries to compensate by throttling back the CPU's. You might, or might not, see messages like the following in the Console window:

SMC::smcHandleInterruptEvent WARNING status=0x0 (0x40 not set) notif=0x0

The timestamps of those messages (if any) indicate the times, since the log was last cleared, when a processor was being throttled because of high temperature.

Note that if the problem is caused by a faulty sensor that reads too high, there may be no actual overheating.

The Apple Hardware Test, though not very reliable, is sometimes able to detect a bad fan or temperature sensor.

Using Apple Hardware Test


Encryption

Transferring large amounts of data to or from an encrypted disk image or FileVault volume puts an extra load on the kernel. If both the source and the destination are encrypted, the load may be doubled. If you transfer data from an encrypted disk image on an encrypted partition to another such image on another encrypted partition, the load may be quadrupled.

This issue probably doesn't affect late-model Macs with an Intel i-series, recent Xeon, or later processor. Those processors support hardware-accelerated encryption. You can determine what kind of processor you have by selectingAbout This Mac from the Apple menu in the menu bar.

Installed software

User-installed software that includes a device driver or other kernel code may thrash the kernel. Some system-monitoring applications, such as "iStat," can also contribute to the problem. You can test for this possibility bycompletely disabling or removing the software according to the developer's instructions, or booting in safe mode (with the shift key held down at the startup chime.) Note, however, that disabling a system modification without removing it or booting in safe mode may not be as easy as you think it is.

Corrupt NVRAM or SMC data

In some cases the issue has reportedly been resolved by resetting the NVRAM or the SMC.

Mid 2011 Macbook Air Painfully slow.

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