From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andreas Ericsson <ae@op5.se>
Cc: "Shawn O. Pearce" <spearce@spearce.org>,
Jakub Narebski <jnareb@gmail.com>,
git@vger.kernel.org
Subject: Re: Request for detailed documentation of git pack protocol
Date: Fri, 15 May 2009 13:29:06 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.01.0905151324280.3343@localhost.localdomain> (raw)
In-Reply-To: <4A0C3282.4000101@op5.se>
On Thu, 14 May 2009, Andreas Ericsson wrote:
> Shawn O. Pearce wrote:
> >
> > In loopback mode for local file URIs, it may become an issue. C Git
> > is just getting lucky by the pipe size I think. Though I thought I
> > read somewhere yesterday pipe FIFOs in Linux were being allocated
> > at 512 bytes, not one system page. Of course other systems could
> > allocate whatever size they want too, and may allocate something
> > below the 2952 minimum, and we'd most likely see a deadlock on them.
> >
>
> Linux allocates one page 4096 bytes for a FIFO. 512 is the maximum
> size guaranteed by POSIX to result in an atomic write.
Actually, modern Linux will allocate up to 16 pages (PIPE_BUFFERS), but
they may not all be filled - we coalesce small writes only if the end
result fits entirely into a page. So the maximum buffer is 16*PAGE_SIZE,
and the minimum buffer space (assuming regular "write()" system calls) is
something like 16*(PAGE_SIZE/2+1).
But yeah, POSIX allows for much smaller buffers.
Linus
next prev parent reply other threads:[~2009-05-15 20:29 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-12 21:29 Request for detailed documentation of git pack protocol Jakub Narebski
2009-05-12 23:34 ` Shawn O. Pearce
2009-05-14 8:24 ` Jakub Narebski
2009-05-14 14:57 ` Shawn O. Pearce
2009-05-14 15:02 ` Andreas Ericsson
2009-05-15 20:29 ` Linus Torvalds [this message]
2009-05-15 16:51 ` Clemens Buchacher
2009-05-14 18:13 ` Nicolas Pitre
2009-05-14 20:27 ` Jakub Narebski
2009-05-14 13:55 ` Scott Chacon
2009-05-14 14:44 ` Shawn O. Pearce
2009-05-14 15:01 ` Jakub Narebski
2009-05-15 0:58 ` A Large Angry SCM
2009-05-15 19:05 ` Ealdwulf Wuffinga
2009-06-02 21:39 ` Jakub Narebski
2009-06-02 23:27 ` Shawn O. Pearce
2009-06-03 0:50 ` Jakub Narebski
2009-06-03 1:29 ` Shawn O. Pearce
2009-06-03 2:11 ` Junio C Hamano
2009-06-03 2:15 ` Shawn O. Pearce
2009-06-03 9:21 ` Jakub Narebski
2009-06-03 14:48 ` Shawn O. Pearce
2009-06-03 15:07 ` Shawn O. Pearce
2009-06-03 15:39 ` Jakub Narebski
2009-06-03 15:50 ` Shawn O. Pearce
2009-06-03 16:51 ` Jakub Narebski
2009-06-03 16:56 ` Shawn O. Pearce
2009-06-03 20:19 ` Jakub Narebski
2009-06-03 20:24 ` Shawn O. Pearce
2009-06-03 22:04 ` Jakub Narebski
2009-06-03 22:04 ` Shawn O. Pearce
2009-06-03 22:16 ` Junio C Hamano
2009-06-03 22:46 ` Jakub Narebski
2009-06-04 7:17 ` Andreas Ericsson
2009-06-04 7:26 ` Junio C Hamano
2009-06-06 16:33 ` Scott Chacon
2009-06-06 17:24 ` Junio C Hamano
2009-06-06 17:41 ` Jakub Narebski
2009-06-03 21:38 ` Tony Finch
2009-06-03 17:11 ` Junio C Hamano
2009-06-03 19:05 ` Johannes Sixt
2009-06-03 2:18 ` Robin H. Johnson
2009-06-03 10:47 ` Jakub Narebski
2009-06-03 14:17 ` Shawn O. Pearce
2009-06-03 20:56 ` Tony Finch
2009-06-03 21:20 ` Jakub Narebski
2009-06-03 21:53 ` Tony Finch
2009-06-04 8:45 ` Jakub Narebski
2009-06-04 11:41 ` Tony Finch
2009-06-04 18:41 ` Shawn O. Pearce
2009-06-03 12:29 ` Jakub Narebski
2009-06-03 14:19 ` Shawn O. Pearce
2009-06-04 20:55 ` Jakub Narebski
2009-06-04 21:57 ` Shawn O. Pearce
2009-06-05 0:45 ` Shawn O. Pearce
2009-06-05 7:24 ` Jakub Narebski
2009-06-05 8:45 ` Jakub Narebski
2009-06-06 21:38 ` Comments pack protocol description in "Git Community Book" (second round) Jakub Narebski
2009-06-06 21:58 ` Scott Chacon
2009-06-07 8:21 ` Jakub Narebski
2009-06-07 20:13 ` Shawn O. Pearce
2009-06-07 20:43 ` Shawn O. Pearce
2009-06-13 9:30 ` Comments pack protocol description in "RFC for the Git Packfile Protocol" (long) Jakub Narebski
2009-06-07 20:06 ` Comments pack protocol description in "Git Community Book" (second round) Shawn O. Pearce
2009-06-09 9:39 ` Jakub Narebski
2009-06-09 14:28 ` Shawn O. Pearce
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