From: Jeff King <peff@peff.net>
To: Michael Haggerty <mhagger@alum.mit.edu>
Cc: "Torsten Bögershausen" <tboegi@web.de>,
"Junio C Hamano" <gitster@pobox.com>,
"David Turner" <dturner@twopensource.com>,
"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Ramsay Jones" <ramsay@ramsayjones.plus.com>,
git@vger.kernel.org
Subject: Re: [PATCH v2 29/33] refs: resolve symbolic refs first
Date: Thu, 12 May 2016 04:25:26 -0400 [thread overview]
Message-ID: <20160512082526.GA20817@sigill.intra.peff.net> (raw)
In-Reply-To: <20160512074528.GB10922@sigill.intra.peff.net>
On Thu, May 12, 2016 at 03:45:28AM -0400, Jeff King wrote:
> So I'd expect us to hit that lock_ref_for_update() for each of the new
> refs. But then we end up in verify_refname_available_dir(), which wants
> to read all of the loose refs again. So we end up with a quadratic
> number of calls to read_ref_full().
>
> I haven't found the actual bug yet. It may be something as simple as not
> clearing REF_INCOMPLETE from the loose-ref cache when we ought to. But
> that's a wild (optimistic) guess.
Ah, nope, nothing so simple.
It looks like we get in a chain of:
1. we want to update a ref, so we end up in
verify_refname_available_dir to make sure we can do so.
2. that has to load all of the loose refs in refs/tags, which is
expensive.
3. we actually update the ref, which calls clear_loose_ref_cache().
And repeat. Each ref update does the expensive step 2, and it gets
larger and larger each time.
I understand why we need to verify_refname_available() on the packed
refs. But traditionally we would rely on EISDIR or EEXIST to detect
conflicts with the loose refs, rather than loading using our own cache.
So I guess that's the new thing that is causing a problem.
-Peff
next prev parent reply other threads:[~2016-05-12 8:25 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 16:13 [PATCH v2 00/33] Yet more preparation for reference backends Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 01/33] t1404: demonstrate a bug resolving references Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 02/33] commit_ref(): if there is an empty dir in the way, delete it Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 03/33] read_raw_ref(): don't get confused by an empty directory Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 04/33] safe_create_leading_directories(): improve docstring Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 05/33] remove_dir_recursively(): add docstring Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 06/33] refname_is_safe(): use skip_prefix() Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 07/33] refname_is_safe(): don't allow the empty string Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 08/33] refname_is_safe(): insist that the refname already be normalized Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 09/33] commit_ref_update(): write error message to *err, not stderr Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 10/33] rename_ref(): remove unneeded local variable Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 11/33] ref_transaction_commit(): remove local variable n Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 12/33] read_raw_ref(): rename flags argument to type Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 13/33] read_raw_ref(): clear *type at start of function Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 14/33] read_raw_ref(): rename symref argument to referent Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 15/33] read_raw_ref(): improve docstring Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 16/33] read_raw_ref(): move docstring to header file Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 17/33] lock_ref_sha1_basic(): remove unneeded local variable Michael Haggerty
2016-05-06 16:13 ` [PATCH v2 18/33] refs: make error messages more consistent Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 19/33] ref_transaction_create(): disallow recursive pruning Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 20/33] ref_transaction_commit(): correctly report close_ref() failure Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 21/33] delete_branches(): use resolve_refdup() Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 22/33] refs: allow log-only updates Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 23/33] refs: don't dereference on rename Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 24/33] verify_refname_available(): adjust constness in declaration Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 25/33] add_update(): initialize the whole ref_update Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 26/33] lock_ref_for_update(): new function Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 27/33] unlock_ref(): move definition higher in the file Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 28/33] ref_transaction_update(): check refname_is_safe() at a minimum Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 29/33] refs: resolve symbolic refs first Michael Haggerty
2016-05-12 7:45 ` Jeff King
2016-05-12 8:25 ` Jeff King [this message]
2016-05-13 12:33 ` Michael Haggerty
2016-05-13 12:35 ` [PATCH v3 " Michael Haggerty
2016-05-13 12:58 ` Jeff King
2016-05-13 12:51 ` [PATCH v2 " Jeff King
2016-05-14 9:02 ` Torsten Bögershausen
2016-05-06 16:14 ` [PATCH v2 30/33] lock_ref_for_update(): don't re-read non-symbolic references Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 31/33] lock_ref_for_update(): don't resolve symrefs Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 32/33] commit_ref_update(): remove the flags parameter Michael Haggerty
2016-05-06 16:14 ` [PATCH v2 33/33] lock_ref_sha1_basic(): only handle REF_NODEREF mode Michael Haggerty
2016-05-09 20:12 ` [PATCH v2 00/33] Yet more preparation for reference backends David Turner
2016-05-09 21:05 ` Junio C Hamano
2016-05-09 21:50 ` Michael Haggerty
2016-05-09 22:04 ` Junio C Hamano
2016-05-12 7:55 ` Jeff King
2016-05-12 16:10 ` Junio C Hamano
2016-05-10 21:32 ` Junio C Hamano
2016-06-10 12:50 ` Michael Haggerty
2016-06-10 15:43 ` Junio C Hamano
2016-06-13 9:55 ` [ADDENDUM v4] " Michael Haggerty
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