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Re: [PATCH 00/20] Read `packed-refs` using mmap()

From
Johannes Schindelin <johannes.schindelin@gmx.de>
Date
Sep 14, 2017, 22:16 UTC
Message-ID
<alpine.DEB.2.21.1.1709150012550.219280@virtualbox>
In-Reply-To
<ef919cc7-7e41-afb6-38b2-e2fae4efcbf1@alum.mit.edu>
Hi Michael,
On Thu, 14 Sep 2017, Michael Haggerty wrote:
Show 8 quoted lines
> On 09/13/2017 07:15 PM, Michael Haggerty wrote:
> > [...]
> > * `mmap()` the whole file rather than `read()`ing it.
> > [...]
>
> Apparently this doesn't work on Windows, because the `snapshot` is
> keeping the `packed-refs` file open too long, so the new file can't be
> renamed on top of it.
Indeed, I sent you a mail about it before I checked for new mails ;-)
> I didn't realize that this is even allowed, but TIL that you can close a
> file while keeping it mmapped. Does that technique work on Windows? If
> so, I'll change v2 to do it as sketched below.

I do not know whether that technique works on Windows, but it would not solve the problem *entirely*, as I outlined in my reply: in delete_branches(), for example, the main_worktree_ref_store is implicitly getting its snapshot initialized, and nothing seems to release it.

This is only one example, as I figure that multiple worktrees could cause even more ref_stores to have unreleased snapshots of the packed-refs file.

I imagine that something like close_all_packs() is needed ("clear_all_snapshots()"?).

Ciao, Dscho

Previous: Michael HaggertyNext: Johannes Schindelin
Message 25 of 27 in “Read `packed-refs` using mmap()”
  1. 00/20 Read `packed-refs` using mmap()Michael Haggerty, Sep 13, 2017
  2. 01/20 ref_iterator: keep track of whether the iterator output is orderedMichael Haggerty, Sep 13, 2017
  3. 02/20 prefix_ref_iterator: break when we leave the prefixMichael Haggerty, Sep 13, 2017
  4. 03/20 packed_ref_cache: add a backlink to the associated `packed_ref_store`Michael Haggerty, Sep 13, 2017
  5. 05/20 read_packed_refs(): use mmap to read the `packed-refs` fileMichael Haggerty, Sep 13, 2017
  6. 06/20 read_packed_refs(): only check for a header at the top of the fileMichael Haggerty, Sep 13, 2017
  7. 07/20 read_packed_refs(): make parsing of the header line more robustMichael Haggerty, Sep 13, 2017
  8. 09/20 packed_ref_cache: remember the file-wide peeling stateMichael Haggerty, Sep 13, 2017
  9. 11/20 mmapped_ref_iterator_advance(): no peeled value for broken refsMichael Haggerty, Sep 13, 2017
  10. 12/20 packed_ref_cache: keep the `packed-refs` file open and mmappedMichael Haggerty, Sep 13, 2017
  11. 17/20 packed_ref_store: get rid of the `ref_cache` entirelyMichael Haggerty, Sep 13, 2017
  12. 19/20 mmapped_ref_iterator: inline into `packed_ref_iterator`Michael Haggerty, Sep 13, 2017
  13. 20/20 packed-backend.c: rename a bunch of things and update commentsMichael Haggerty, Sep 13, 2017
  14. Stefan BellerSep 13, 2017
  15. 14/20 packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator`Michael Haggerty, Sep 13, 2017
  16. 18/20 ref_cache: remove support for storing peeled valuesMichael Haggerty, Sep 13, 2017
  17. 10/20 mmapped_ref_iterator: add iterator over a packed-refs fileMichael Haggerty, Sep 13, 2017
  18. 15/20 packed_read_raw_ref(): read the reference from the mmapped bufferMichael Haggerty, Sep 13, 2017
  19. 16/20 ref_store: implement `refs_peel_ref()` genericallyMichael Haggerty, Sep 13, 2017
  20. 04/20 die_unterminated_line(), die_invalid_line(): new functionsMichael Haggerty, Sep 13, 2017
  21. 13/20 read_packed_refs(): ensure that references are ordered when readMichael Haggerty, Sep 13, 2017
  22. 08/20 read_packed_refs(): read references with minimal copyingMichael Haggerty, Sep 13, 2017
  23. Junio C HamanoSep 13, 2017
  24. Michael HaggertySep 14, 2017
  25. Johannes SchindelinSep 14, 2017
  26. Johannes SchindelinSep 14, 2017
  27. Michael HaggertySep 15, 2017

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