From: Linus Torvalds <torvalds@osdl.org>
To: Marco Costalba <mcostalba@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
Junio C Hamano <junkio@cox.net>, Alex Riesen <raa.lkml@gmail.com>,
Shawn Pearce <spearce@spearce.org>
Subject: Re: [RFC \ WISH] Add -o option to git-rev-list
Date: Sun, 10 Dec 2006 14:16:30 -0800 (PST) [thread overview]
Message-ID: <Pine.LNX.4.64.0612101410220.12500@woody.osdl.org> (raw)
In-Reply-To: <e5bfff550612101405h507cc877k87491264d11b0aa8@mail.gmail.com>
On Sun, 10 Dec 2006, Marco Costalba wrote:
>
> Ok. Perhaps I'm doing something wrong but the following code it's
> always 10% slower then the temporary file one (4.7s against 4.3s for
> linux tree)
Why do you seem to be doing a "new" on every iteration inside the loop?
Also, why do you have that strange FILE_BLOCK_SIZE thing, and in
particular the "if (len < FILE_BLOCK_SIZE)" check? One thing that pipes vs
files do is the blocking factor.
Especially with older kernels, I _guarantee_ you that you'll only ever get
4kB at a time, so because of that "if (len < 64kB) break" thing, the only
thing you're doing is to make sure things suck performance-wise, and you
won't be reading the rest of the data until 100ms later.
IOW, your code is written for a file, and makes no sense there either
(checking "feof(file)" is wrong, since you may well have hit the EOF
*at*that*time*, but the file may GROW since you are doing it all in the
background, so you can't rely on feof() anyway).
For a pipe, what you should do is to make sure it's in nonblocking mode,
and just continue reading until it gets no more. And instead of using a
timeout, you should use poll() or something to get notified when there is
more data.
IOW, the reason it's slow is because you're doing the wrong thing.
next prev parent reply other threads:[~2006-12-10 22:16 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-10 11:38 [RFC \ WISH] Add -o option to git-rev-list Marco Costalba
2006-12-10 14:54 ` Alex Riesen
2006-12-10 18:16 ` Linus Torvalds
2006-12-10 19:51 ` Marco Costalba
2006-12-10 20:00 ` globs in partial checkout? Michael S. Tsirkin
2006-12-10 20:13 ` Linus Torvalds
2006-12-10 21:07 ` Michael S. Tsirkin
2006-12-10 20:08 ` [RFC \ WISH] Add -o option to git-rev-list Linus Torvalds
2006-12-10 20:19 ` Linus Torvalds
2006-12-10 22:05 ` Marco Costalba
2006-12-10 22:09 ` Marco Costalba
2006-12-10 22:16 ` Linus Torvalds [this message]
2006-12-10 22:35 ` Marco Costalba
2006-12-10 22:53 ` Linus Torvalds
2006-12-11 0:15 ` Marco Costalba
2006-12-11 0:51 ` Linus Torvalds
2006-12-11 7:17 ` Marco Costalba
2006-12-11 10:00 ` Alex Riesen
2006-12-11 16:59 ` Linus Torvalds
2006-12-11 17:07 ` Linus Torvalds
2006-12-11 17:39 ` Marco Costalba
2006-12-11 18:15 ` Linus Torvalds
2006-12-11 18:59 ` Marco Costalba
2006-12-11 19:25 ` Linus Torvalds
2006-12-11 20:28 ` Josef Weidendorfer
2006-12-11 20:40 ` Linus Torvalds
2006-12-11 20:54 ` Josef Weidendorfer
2006-12-11 21:14 ` Linus Torvalds
2006-12-15 18:45 ` Marco Costalba
2006-12-15 19:20 ` Linus Torvalds
2006-12-15 20:41 ` Marco Costalba
2006-12-15 21:04 ` Marco Costalba
2006-12-11 9:26 ` Josef Weidendorfer
2006-12-11 12:52 ` Marco Costalba
2006-12-11 13:28 ` Josef Weidendorfer
2006-12-11 17:28 ` Marco Costalba
2006-12-11 11:39 ` Andreas Ericsson
2006-12-11 12:59 ` Marco Costalba
2006-12-11 13:40 ` Andreas Ericsson
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