Re: "ls -l": Avoid unnecessary getxattr() overhead

[Sven Breuner]

Jim Meyering wrote on 02/09/2012 04:08 PM:
> I'm not as enthusiastic about adding code to optimize away
> the calls in file_has_acl, unless there are mainstream system/FS
> for which it makes a difference.

Jim Meyering wrote on 02/09/2012 03:17 PM:
> Here's that simpler patch:
>
> diff --git a/src/ls.c b/src/ls.c
> index f5cd37a..cb9f834 100644
> [...]


Does cifs count as mainstream in this context?

Here's a test run on rhel 6.2 (one machine exporting an ext4, the other 
one mounting via cifs with default settings), selinux_challenged_device 
patch already applied to ls:

$ strace -c ~/tmp/ls-8.15.34-31eee_patched -l >/dev/null
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 44.56    0.186147           3     61440           lstat
 38.94    0.162680           3     61440     61440 getxattr
 15.80    0.065989         122       540           getdents
[...]

While this kind of large directory might not be very typical as a use 
case for cifs, I know at least quite a few cifs filer admins that would 
be happy about every single network request they could keep off of their 
filers to reduce load.

On the other hand, you say you don't feel enthusiastic about such a 
change, so you probably have good reasons for that (I have to admit I 
didn't take a closer look at that code yet).

Best regards,
Sven