I'm trying to analyze some mini crash dumps. I'm using Windows 10 Pro Build 1607 and WinDbg 10.0.14321.1024. I have my symbol file path set to
SRV*C:\SymCache*https://msdl.microsoft.com/download/symbols
Basically, whenever I load up a minidump (all < 1 MB .dmp files), it takes WinDbg forever to actually analyze them. I understand the first run can take long, but it took mine almost 12 hours before it would let me enter a command. I assumed that, since the symbols were cached, it wouldn't take long at all to re-open the same .dmp. This is not the case. It loads up, goes pretty much instantaneously to "Loading Kernel Symbols", then takes another 30 minutes before it prints the "BugCheck" line. It's been another 30 minutes, and I still can't enter commands into it.
My PC has a 512 GB SSD, 8 GB of RAM, and an i5-4590. I don't think it should be this slow.
What am I doing wrong?
These kind of complaints seem to occur more often lately and I can reproduce it on my PC. This is not your fault but some issue with the Internet or the symbol server on Microsoft side.
Monitoring the traffic with Wireshark and looking at my disk on how the symbol cache get populated, I can say:
only one file is being downloaded at a time.
the problem also occurs with older WinDbg versions (6.2.9200)
the problem occurs with HTTP and HTTPS
when symbols are found, the transfer speed is very slow, then increasing. The effective transfer rate is down at 11 kb/s to 20 kb/s (on a line which can handle 6500 kb/s)
there's quite a high number of packets out of order, duplicate packets etc., especially during the "lookup phase" where no file is downloaded yet. Such a lookup phase can easily take 8 minutes.
even if the file already exists on disk, the "lookup phase" is performed.
the HTTP roundtrip time (request to response) is 8 to 9 seconds
This is the symbol server being really slow. Other have noticed as well: https://twitter.com/BruceDawson0xB/status/772586358556667904
Your symbol path contains a local cache so it should load faster next time around, but it seems that the cache is not effective, I can't tell really why (I suspect the downloaded symbols are not a perfect match and they are being downloaded again, every time).
I would recommend modifying the _NT_SYMBOL_PATH (or whatever is the way your sympath is initialized) to SRV*C:\SymCache only, ie. do not attempt to automatically download, just use the symbols you already have cached locally. The image should open fairly fast. Only enable the symbols server if you discover missing symbols.
I ran into the same problem (extremely slow windbg), but loading/reloading/fixing/caching symbols did not help. By accident, I figured out that this problem persists when I try to print memory with address taken from a register, like
db rax
The rule of thumb is to always use # with the register name.
db #rax
Without this symbol, the debugger considers rax to be a symbol name, and looks for it some time (depending on the amount of symbols you have loaded) and fails to find it eventually, and falls back to treating it like a register name. Printing memory from register with # symbol works instantly, even if you have gigs of symbols loaded in memory. As you can see, this problem is also symbol-related, but in a different way.
Related
I'm trying to use a perl program on a Windows HTCondor computing cluster. The way HTCondor on windows works is it copies all dependencies into a temporary directory (used as a chroot of sorts) and then it deletes the directory after the specified outputs are moved to a designated place.
If I take only perl.exe and perl514.dll and make a job like this: perl -e "print qq/hello\n/" and tell the cluster to run it 200 times, then each replication winds up taking about 15 seconds, which is acceptable overhead. That's almost all time spent repeatedly copying the files over the network and then deleting them. echo_hello.bat run 200 times takes more like two seconds per replication.
The problem I have is that when I try to use my full blown perl distribution of 55MB and 2,289 files, a single "hello" rep takes something like four minutes of copying and deleting, which is unacceptable. When I try to do many runs the disks on the machines grind to a halt trying to concurrently handle all the file operations across all the reps, so it doesn't work at all. I don't know how long it might take to eventually finish because I gave up after half an hour and no jobs had finished.
I figured PAR::Packer might fix the issue, but nope. I tried print_hello.exe created like this: pp -o print_hello.exe -e "print qq/hello\n/". It still makes things grind to a halt, apparently by swamping the filesystem. I think a PAR::Packer executable makes a ton of temporary files as it pulls out files it needs from the archive. I think the windows file system totally chokes when there are a bunch of concurrent small file operations.
So how can I go about cutting down the perl I built to something like 6MB and a dozen files? I'm really only using a tiny number of core modules and don't need most of the crap in bin and lib, but I have no idea how to proceed ripping out stuff in a sane way.
Is there an automated way to strip away un-needed files and modules?
I know TCL has a bunch of facilities for packing files into a single uncompressed archive that can then be accessed through a "virtual filesystem" without expanding the file. Is there some way to do this with perl itself sort of like with PAR? The problem is PAR compresses everything and then has to extract to temporary files, rather than directly work through a virtual filesystem layer. (If I understand correctly.)
My usage of perl is actually as a scripting layer. It's embedded in a simulation. So I'm really running my_simulation.exe which depends on per514.dll, but you get the idea. I also cannot realistically do anything to the HTCondor cluster other than use it. So there's no need to think outside the box on what I should be using instead of perl and what I could administratively tweak in Windows and HTCondor, thanks.
You can use Module::ScanDeps to get list of actual dependencies of your perl. It was terrible, that it took significant amount of time, when PAR::Packer unpacked the whole application, so I decided to build the executable by myself.
Here is my ready to use script which gathers perl dependencies into some directory; it might be useful for you to reduce the number of perl-modules, e.g. by manually removing some dependencies after copying.
In theory (I have never tried that), the next your step could be merge all pure-perl dependencies into single file (like deps.pm); although it might be non-trivial due to perl's autoload magic and some other tricks.
You can list the modules that are needed by your program using the very nice ListDependencies module
To my knowledge it isn't downloadable anywhere, but it is simple to copy and paste into your own ListDependencies.pm file
You should read the POD documentation within the module for usage instructions
Emacs 24 in Ubuntu 14.
I have file opened only in emacs, and it gives me this constantly, after each saving. that is annoying.
This is strange, because earlier everything worked fine. I can hardly guess what could I break during this time. I'am total newbie in Ubuntu, using it according to instructions found in internet.
Now I'm using emacs 23, everything is fine. I guess, I need auto-syncronization of opened buffer with saved file right after saving. Anyway, how can I fix it?
It sounds like some other program on your computer is reading the file when it changes, and possibly even introducing changes (perhaps just to the modification time, rather than to the contents). It's hard to say off-hand just what that would be.
A workaround try M-x global-auto-revert-mode. It will only auto-revert if you have no local modification since the last saving. This is generally a nice mode to turn on if you use multiple editors, and I keep it enabled all the time.
Other ideas:
Check if any other process currently has the file open using fuser /path/to/filename.txt (note: it only shows open file descriptors, not processes that hold the file content in memory and write it later)
Do you use any non-standard filesystem? (check with df -h /path/to/filename.txt and mount)
Is your system time stable? (Manually check date, scan the output of dmesg for obvious errors concerning timekeeping, and look for errors related to NTP in the logfiles in /var/log/.
I have a data file (6.3GB) that I'm attempting to work on in MATLAB, but I'm unable to get it to load, and I think it may be a memory issue. I've tried loading in a smaller "sample" file (39MB) and that seems to work, but my actual file won't load at all. Here's my code:
filename = 'C://Users/Andrew/Documents/filename.mat';
load(filename);
??? Error using ==> load
Can't read file C://Users/Andrew/Documents/filename.mat.
exist(filename);
EDU>> ans = 2
Well, at least the file exists. When I check the memory...
memory
Maximum possible array: 2046 MB (2.146e+009 bytes) *
Memory available for all arrays: 3442 MB (3.609e+009 bytes) **
Memory used by MATLAB: 296 MB (3.103e+008 bytes)
Physical Memory (RAM): 8175 MB (8.572e+009 bytes)
* Limited by contiguous virtual address space available.
** Limited by virtual address space available.
So since I have enough RAM, do I need to increase the maximum possible array size? If so, how can I do that without adding more RAM?
System specifics: I'm running 64-bit Windows, 8GB of RAM, MATLAB Version 7.10.0.499 (R2010a). I think I can't update to a newer version since I'm on a student license.
As the size might be the issue, you could try load('fileName.mat', 'var1'); load('fileName.mat', 'var2'); etc. For this, you'll have to know the variable names though.
An option would be to use the matfile object to load/index directly into the file instead of loading into ram.
doc matfile
But one limitation is that you can not index directly into a struct. So you would need to find a friend to convert the struct in your mat file and save it with the version option
save(filename, variables, '-v7.3')
May be you can load part by part your data to do your stuff using load part of variables from mat file. You must have matlab 7.3 or newer.
From your file path I can see you are using Windows. Matlab is only 32 bit for Windows and Linux (there is no 64 bit for these OSes at least for older releases, please see my edit), which means you are limited to <4GB ram total for a single application (no matter how much you have in your system), this is a 32 bit application issue so there is nothing you can do to remedy it. Interestingly the Mac version is 64 bit and you can use as much ram as you want (in my computer vision class we often used my mac to do our big video projects because windows machines would just say "out of memory")
As you can see from your memory output you can only have ~3.4GB total for matrix storage, this is far less than the 6.3GB file. You'll also notice, you can only use ~2GB for one particular matrix (that number changes as you use more memory).
Typically when working with large files you can read the file line by line, rather than loading the entire file into memory. But since this is a .mat file that likely wouldn't work. If the file contains multiple variables maybe separate them each into their own individual files that are small enough to load
The take home message here is you can't read the entire file at once unless you hop onto a Mac with enough RAM. Even then the size for a single matrix is still likely less than 6.3GB
EDIT
Current Matlab student versions can be purchased in 64 bit for all OSes as of 2014 see here so a newer release of Matlab might allow you to read the entire file at once. I should also add there has been a 64 bit version before 2014, but not for the student license
I have noticed that MATLAB (R2011b on Windows 7, 64 bit) tends to slow down if I am in debugging mode for a long period of time (e.g. 3 hours). I don't recall this happening on previous versions of MATLAB.
The slow down is small, but significant enough to have an impact on my productivity (sometimes MATLAB needs to wait for up to 1 sec before I can type on the command line or on the editor).
I usually spend hours on debugging mode (e.g. after stopping at a keyboard statement) coding full projects in this mode. I find working on debugging mode convenient to organically grow my code while inspecting my code anytime in execution time.
The odd thing is my machine has 16 GB of RAM and the total size of all workspaces while in debugging mode is usually less than 4 GB. I don't have any other large process running in the background, and my system reports ~8GB of free RAM.
Also, unfortunately MATLAB does not let me call pack from debugging mode; it complains with :
Warning: PACK can only be used from the MATLAB command line.
I have reproduced this behavior after restarting MATLAB, rebooting my system, and on different days. With this, my question/s are:
Has anybody else noticed this? Is there anything I could do to prevent this slowdown without exiting debugging mode?
Are there any technical notes or statements from Mathworks addressing this issue?
In case it matters, my code is on a network drive, so I added the following on my startup.m file, which should alleviate any impact on performance resulting from it:
system_dependent('RemoteCWDPolicy', 'None');
system_dependent('RemotePathPolicy', 'None');
system_dependent('DirChangeHandleWarn','Never');
I have experienced some similar issues. The problem ended up being that Mathworks changed how Matlab caches files. For some users, it is now storing data in the TMP folder as defined by the environment variables. This folder was being scanned by anti virus and causing a lot of performance problem. Of course, IT wouldn't let us exclude the TMP folder from scans. So we added a line to our start up script that changes the environment variable of TMP to some other location within an excluded folder.
You don't have to worry about changing the variable back or messing up other programs. When applications launch, they copy the environment variables into their own local instance of them. Any changes made to them only change the local copy of those variables, not the system copy.
Here is the function you will need.
setenv('TEMP', 'C:\TEMP');
I'm not sure if it was TMP or TEMP. Check your environment variables to be sure.
I am using MATLAB R2011 on linux 10, windows 7 (32 bit).
I experienced MATLAB slowing down while printing simple variables in command window.
It turned that there was one .m file loaded in my Editor.
It was a big file with 10000 lines. These lines were simple data that should have been saved as mat file. When i closed this file, the editor was back to its normal speed.
I'm wondering whether I will ever get a different result when producing a checksum on an .exe file before and then while or after running that file. I'm more concerned with common practice (such as producing a SHA hash of popular app like firefox.exe) than with boundary cases, but both are interesting. Thanks.
The hash of a file should be constant for as long as the file is identical (i.e. contains only the same bytes, in the same order). It's very rare to find applications that rewrite their on-disk representation at runtime, so the hash should be constant. There are self-modifying programs, but they tend to operate on the in-memory loaded copy of their code, rather than the disk copy.
Edit: We should consider "Self-updating" applications, but these tend to launch a little helper program to download and update the core application. It's difficult (especially on Windows) to update an execution whilst it's running. UNIX systems tend to operate Copy on Write systems, so it's possible that a software update might change your executable under your feet - but again, this is a "corner case".
The hash will only change if the exe changes. That will only happen if the app modifies itself, which isn't going to happen on windows without the app restarting. Firefox might update itself (including a restart), but apart from such cases, the hash will remain the same.
The hash will change if the file changes.
EXE files rarely change on their own. firefox.exe would change if the user updates to a new version.
You can check the "date modified" attribute of an EXE file (like firefox.exe) after running it to see whether it has changed, but you'll probably find it hasn't.
If you mean the modification of the last access time, don't worry, it's stored at the filesystem level, not within the file so the hash will remain the same.