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git: runtime error R6016 - not enough space for thread data #966
Description
We are seeing this error at random times when running git commands like "git rebase", "git push", and "git pull".
Some examples:
Z:\o2\src>git rebase origin/lkg/word/dev
Receiving packfile 1/1 with 35 objects (bytes received): 807627, done.
Successfully rebased and updated refs/heads/user/tiagoma/spaceship_FormatLineKey.
runtime error R6016
- not enough space for thread data
d:\offgit\src\engtoolsrs>git pull
Prefetch 1784815572 (2026-07-23 14:06:12 +0000) (bytes received): 2873445, done.
Extracting prefetch packfiles: 100% (1/1), done.
Installing prefetch packfiles: 100% (1/1), done.
From https://dev.azure.com/Office/Office/_git/Office
- [deleted] (none) -> origin/build/main/16.0.20023.15070
(lots of lines removed)
fed835f176025..536e118c3b4fc release/office/perpetualvl/2021 -> origin/release/office/perpetualvl/2021
runtime error R6016
- not enough space for thread data
Updating c610e205d58df..42f46e4299052
Receiving packfile 1/1 with 5 objects (bytes received): 20132, done.
Fast-forward
d:\offgit\src\otools\deps\pkgsets\common>git push
Enumerating objects: 14, done.
Counting objects: 100% (14/14), done.
Path-based delta compression using up to 64 threads
Compressing objects by path: 100% (14/14), done.
Delta compression using up to 64 threads
Compressing objects: 100% (1/1), done.
Writing objects: 100% (7/7), 839 bytes | 279.00 KiB/s, done.
Total 7 (delta 6), reused 0 (delta 0), pack-reused 0 (from 0)
runtime error R6016
- not enough space for thread data
remote: Analyzing objects... (7/7) (46 ms)
remote: Validating commits... (1/1) done (13 ms)
remote: Checking for reserved names in refs, blobs and trees... done (26 ms)
remote: Checking for restricted file names... done (39 ms)
remote: Checking path lengths for refs and files... done (52 ms)
remote: Checking path lengths for refs and files... done (65 ms)
remote: Checking for credentials and other secrets... done (130 ms)
remote: Checking commit author emails... (1/1) done (147 ms)
remote: Storing packfile... done (37 ms)
remote: Storing index... done (76 ms)
remote: Updating refs... done (475 ms)
To https://dev.azure.com/Office/Office/_git/Office
* [new branch] user/michmarc/DeployScoper -> user/michmarc/DeployScoper
branch 'user/michmarc/DeployScoper' set up to track 'origin/user/michmarc/DeployScoper'.
Activity
derrickstolee commentedon Jul 23, 2026
This is hinting towards issues allocating memory which may be the correct root cause of the issue informing #956.
dscho commentedon Jul 24, 2026
I don't see which Git version was used; To make sure that we're not chasing a bug that has already been fixed, please try to reproduce with https://github.com/microsoft/git/releases/tag/v2.55.0.vfs.0.3
derrickstolee commentedon Jul 24, 2026
At least one users is on v2.55.0.vfs.0.2 because of the trace2 die recursion issue hitting them previously. This is giving more credence to
mallocbeing the real problem (not the time function) that motivated #956.dscho commentedon Jul 27, 2026
v2.55.0.vfs.0.3 is now marked as the latest version. Dorothy Hung (@Dorothyhung) did it fix your problem?
derrickstolee commentedon Jul 28, 2026
Johannes Schindelin (@dscho): Do you have reason to believe that something about memory allocation changed between .0.2 and .0.3?
I vaguely remember that some malloc changes were happening in git-for-windows/git recently. How could we investigate this line of thinking to assist? It's tricky because our internal customers are reporting these issues, but we have not been able to reproduce them consistently.
dscho commentedon Jul 28, 2026
I misunderstood your comment to mean that this might be fixed in v2.55, sorry.
Yes, we removed
mimalloc. I'll prepare a PR to reinstate it so that we can test.