Re: Slow "symbol-file" when using GDB 12.1 on Windows hosts

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 17 Mar 2023 17:29:27 +0000
> From: Luis Machado <luis.machado@arm.com>
> 
> On 3/15/23 15:50, Adrian Oltean via Gdb wrote:
> > Hi,
> > 
> > We recently upgraded the GDB version (from 10.3 to 12.1) in one of our IDEs and
> > found a painful performance issue on some Windows-based machines. I used
> > Process Monitor to identify the events that occur during a "symbol-file" invocation.
> > This is the command that now (GDB 12.1) seems to take ~2 seconds in the most
> > favorable case, and ~20 seconds in the worst case (on some machines). Note that
> > this happens with basic/small ELF files. Moreover, in GDB 10.3 execution of
> > "symbol-file" is almost instant.
> > 
> > The relevant list of events reported by Process Monitor is the following:
> > Time of Day,Process Name,PID,Operation,Path,Result,Detail
> > 43:02.7, arm-none-eabi-gdb.exe, 13604, ReadFile, C:\MyIDE\workspace\MyProject\Debug\MyProject.axf, SUCCESS, "Offset: 272,405, Length: 512"
> > 43:02.7, arm-none-eabi-gdb.exe, 13604, CreateFile, C:\MyIDE\workspace\MyProject\Debug , SUCCESS, "Desired Access: Read Data/List Directory, Synchronize, Disposition: Open, Options: Directory, Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a, OpenResult: Opened"
> > 43:02.7, arm-none-eabi-gdb.exe, 13604, QueryDirectory,C:\MyIDE\workspace\MyProject\Debug\MyProject.axf.dwp, NO SUCH FILE, "FileInformationClass: FileBothDirectoryInformation, Filter: MyProject.axf.dwp"
> > 43:02.7, arm-none-eabi-gdb.exe, 13604, CloseFile, C:\MyIDE\workspace\MyProject\Debug,SUCCESS,
> > 43:02.7, arm-none-eabi-gdb.exe, 13604, CreateFile, C:\MyIDE\workspace\MyProject\Debug\Users\MyUsername\Documents\MyIDE\workspace\MyProject\Debug\, PATH NOT FOUND, "Desired Access: Read Data/List Directory, Synchronize, Disposition: Open, Options: Directory, Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a"
> > 43:02.7, arm-none-eabi-gdb.exe, 13604, CreateFile, C:\Users\MyUsername\Users\MyUsername\Documents\MyIDE\workspace\MyProject\Debug\, PATH NOT FOUND, "Desired Access: Read Data/List Directory, Synchronize, Disposition: Open, Options: Directory, Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a"
> > 43:05.9, arm-none-eabi-gdb.exe, 13604, CreateFile, C:\Windows\CSC\v2.0.6\namespace\lib, NAME NOT FOUND, "Desired Access: Read EA, Write EA, Read Attributes, Write Attributes, Delete, Read Control, Synchronize, Disposition: Open, Options: Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a"
> > 43:05.9, arm-none-eabi-gdb.exe, 13604, CreateFile, \\lib\debug\Users\MyUsername\Documents\MyIDE\workspace\MyProject\Debug\,BAD<file://lib/debug/Users/MyUsername/Documents/MyIDE/workspace/MyProject/Debug/,BAD> NETWORK PATH, "Desired Access: Read Data/List Directory, Synchronize, Disposition: Open, Options: Directory, Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a"
> > 43:05.9, arm-none-eabi-gdb.exe, 13604, CreateFile, C:\Windows\CSC\v2.0.6\namespace\lib, NAME NOT FOUND, "Desired Access: Read EA, Write EA, Read Attributes, Write Attributes, Delete, Read Control, Synchronize, Disposition: Open, Options: Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a"
> > 43:05.9, arm-none-eabi-gdb.exe, 13604, CreateFile, C:\MyIDE\workspace\MyProject\Debug, SUCCESS, "Desired Access: Read Data/List Directory, Synchronize, Disposition: Open, Options: Directory, Synchronous IO Non-Alert, Attributes: n/a, ShareMode: Read, Write, Delete, AllocationSize: n/a, OpenResult: Opened"
> > 43:05.9, arm-none-eabi-gdb.exe, 13604, QueryDirectory, C:\MyIDE\workspace\MyProject\Debug\MyProject.axf.dwp, NO SUCH FILE, "FileInformationClass: FileBothDirectoryInformation, Filter: MyProject.axf.dwp"
> > 
> > I see attempts to read files/folders that aren't actually present on my machine. Also,
> > a folder like "C:\Windows\CSC" (see "C:\Windows\CSC\v2.0.6\namespace\lib" above) isn't
> > accessible on my machine without admin privileges (I don't have this, according to
> > company policy). I observe that an attempt to access such a file/folder (or a network-specific
> > path) hangs GDB for a few seconds. Questions:
> > 
> >    1.  Is GDB trying to find debug symbols in all those folders? Or what's with them?
> >    2.  What is the code from GDB that artificially builds all those paths?
> >    3.  GDB 10.2 does not seem to access "C:\Windows\CSC\v2.0.6\namespace\lib", nor
> > "\\lib\debug\Users\MyUsername\...<file://lib/debug/Users/MyUsername/...>". Is this related to a recent change? Can someone
> > point to the relevant change in this case?
> > 
> >    1.  Is there a command to stop GDB from attempting to access those files/folders?
> > 
> > Thank you,
> > Adrian
> 
> I vaguely remember Eli ran into Windows-hosted gdb slowdowns before, but I'm not sure if it is related
> to what's been described here.
> 
> Eli?

That problem was solved.  And it was with GDB 13, not GDB 12.

I actually am not sure the fact that GDB looks in several directories
has anything to do with slowdown in symbol-file.  The timeline
presented by the OP shows just one directory accessing which allegedly
takes 3 seconds, and I'm not sure what to make of that.  In any case,
showing elapsed time on a modern system doesn't constitute a clear
evidence that there's some heavy processing involved.

I guess what I'm saying is that more information is needed, perhaps
with profile-quality timing data, to see what is going on here and
what could cause a slowdown.