too many lstat() syscalls, therefore too many IOPS

[Andrei Enshin]

Hi rdiff-backup folks,
 
Since recent, during backing up I can see spike in IOPS up to 500 which exhaust 
limit of a VM. Therefore backup process takes very long. I've straced a bit and 
what I can see is: many failed  lstat() syscalls:
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 42.71    0.040247           9      4608      1420 lstat
 35.41    0.033370          12      2860           getdents
  9.41    0.008865           6      1431           open
  4.63    0.004363           3      1430           close
  4.03    0.003797           3      1431           fstat
  3.75    0.003536           2      1417           getuid
  0.04    0.000039          39         1           unlink
  0.01    0.000013           1         9           read
------ ----------- ----------- --------- --------- ----------------
100.00    0.094230                 13187      1420 total
Seems rdiff-backup checks existence of some file/dir:
10:13:16 lstat("/some/path/rdiff-backup-data/increments/foo/bar", 
0x7ffd832fa810) = -1 ENOENT (No such file or directory) <0.000020>
After backup is done, there is still no such file.
Seems the part in path -  /rdiff-backup-data/increments/ - is some "config" for 
rdiff-backup and probably it tryies to find something but can't?

What might be wrong in my setup? What would you recommend to check to solve the 
issue if it is issue at all?
 
---
Best Regards,
Andrei Enshin