From: Eric Sunshine <sunshine@sunshineco.com>
To: Brandon Casey <bcasey@nvidia.com>
Cc: Git List <git@vger.kernel.org>,
Junio C Hamano <gitster@pobox.com>,
Shawn Pearce <spearce@spearce.org>,
Brandon Casey <drafnel@gmail.com>
Subject: Re: [PATCH] sha1_file: introduce close_one_pack() to close packs on fd pressure
Date: Tue, 30 Jul 2013 03:51:59 -0400 [thread overview]
Message-ID: <CAPig+cR68PQ62JC266iGBidD-udBq2BaL-BWaTpY1JkWWBOp0Q@mail.gmail.com> (raw)
In-Reply-To: <1375157113-608-1-git-send-email-bcasey@nvidia.com>
On Tue, Jul 30, 2013 at 12:05 AM, Brandon Casey <bcasey@nvidia.com> wrote:
> When the number of open packs exceeds pack_max_fds, unuse_one_window()
> is called repeatedly to attempt to release the least-recently-used
> pack windows, which, as a side-effect, will also close a pack file
> after closing its last open window. If a pack file has been opened,
> but no windows have been allocated into it, it will never be selected
> by unuse_one_window() and hence its file descriptor will not be
> closed. When this happens, git may exceed the number of file
> descriptors permitted by the system.
>
> This latter situation can occur in show-ref or receive-pack during ref
> advertisement. During ref advertisement, receive-pack will iterate
> over every ref in the repository and advertise it to the client after
> ensuring that the ref exists in the local repository. If the ref is
> located inside a pack, then the pack is opened to ensure that it
> exists, but since the object is not actually read from the pack, no
> mmap windows are allocated. When the number of open packs exceeds
> pack_max_fds, unuse_one_window() will not able to find any windows to
s/not able/not be able/
...or...
s/not able to find/not find/
> free and will not be able to close any packs. Once the per-process
> file descriptor limit is exceeded, receive-pack will produce a warning,
> not an error, for each pack it cannot open, and will then most likely
> fail with an error to spawn rev-list or index-pack like:
>
> error: cannot create standard input pipe for rev-list: Too many open files
> error: Could not run 'git rev-list'
>
> This is not likely to occur during upload-pack since upload-pack
> reads each object from the pack so that it can peel tags and
> advertise the exposed object. So during upload-pack, mmap windows
> will be allocated for each pack that is opened and unuse_one_window()
> will eventually be able to close unused packs after freeing all of
> their windows.
>
> When we have file descriptor pressure, in contrast to memory pressure,
> we need to free all windows and close the pack file descriptor so that
> a new pack can be opened. Let's introduce a new function
> close_one_pack() designed specifically for this purpose to search
> for and close the least-recently-used pack, where LRU is defined as
>
> * pack with oldest mtime and no allocated mmap windows or
> * pack with the least-recently-used windows, i.e. the pack
> with the oldest most-recently-used window
>
> Signed-off-by: Brandon Casey <drafnel@gmail.com>
next prev parent reply other threads:[~2013-07-30 7:52 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-30 4:05 [PATCH] sha1_file: introduce close_one_pack() to close packs on fd pressure Brandon Casey
2013-07-30 7:51 ` Eric Sunshine [this message]
2013-07-30 15:39 ` Junio C Hamano
2013-07-30 19:52 ` Jeff King
2013-07-30 22:59 ` Brandon Casey
2013-07-31 19:51 ` [PATCH v2 1/2] " Brandon Casey
2013-07-31 19:51 ` [PATCH 2/2] Don't close pack fd when free'ing pack windows Brandon Casey
2013-07-31 21:08 ` Antoine Pelisse
2013-07-31 21:21 ` Fredrik Gustafsson
2013-07-31 21:31 ` Brandon Casey
2013-07-31 21:44 ` Fredrik Gustafsson
2013-07-31 21:23 ` Brandon Casey
2013-07-31 21:28 ` Thomas Rast
2013-08-01 17:12 ` [PATCH v2 1/2] sha1_file: introduce close_one_pack() to close packs on fd pressure Junio C Hamano
2013-08-01 18:01 ` Brandon Casey
2013-08-01 18:39 ` Junio C Hamano
2013-08-01 19:16 ` Brandon Casey
2013-08-01 19:23 ` Brandon Casey
2013-08-01 20:02 ` Junio C Hamano
2013-08-01 20:37 ` Brandon Casey
2013-08-02 5:36 ` [PATCH v3] " Brandon Casey
2013-08-02 16:26 ` Junio C Hamano
2013-08-02 17:12 ` Brandon Casey
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAPig+cR68PQ62JC266iGBidD-udBq2BaL-BWaTpY1JkWWBOp0Q@mail.gmail.com \
--to=sunshine@sunshineco.com \
--cc=bcasey@nvidia.com \
--cc=drafnel@gmail.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=spearce@spearce.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).