Re: [RFC \ WISH] Add -o option to git-rev-list

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To: Marco Costalba <mcostalba@...>
Cc: Git Mailing List <git@...>, Junio C Hamano <junkio@...>, Alex Riesen <raa.lkml@...>, Shawn Pearce <spearce@...>
Date: Sunday, December 10, 2006 - 6:16 pm

On Sun, 10 Dec 2006, Marco Costalba wrote:

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.

		Linus
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Messages in current thread:
[RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Sun Dec 10, 7:38 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Sun Dec 10, 2:16 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Sun Dec 10, 3:51 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Andreas Ericsson, (Mon Dec 11, 7:39 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Mon Dec 11, 8:59 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Andreas Ericsson, (Mon Dec 11, 9:40 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Sun Dec 10, 4:08 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Sun Dec 10, 4:19 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Sun Dec 10, 6:05 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Sun Dec 10, 6:16 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Sun Dec 10, 6:35 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Sun Dec 10, 6:53 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Sun Dec 10, 8:15 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Josef Weidendorfer, (Mon Dec 11, 5:26 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Mon Dec 11, 8:52 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Josef Weidendorfer, (Mon Dec 11, 9:28 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Mon Dec 11, 1:28 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Sun Dec 10, 8:51 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Mon Dec 11, 3:17 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Mon Dec 11, 12:59 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Mon Dec 11, 1:07 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Mon Dec 11, 1:39 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Mon Dec 11, 2:15 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Mon Dec 11, 2:59 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Josef Weidendorfer, (Mon Dec 11, 4:28 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Mon Dec 11, 4:40 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Josef Weidendorfer, (Mon Dec 11, 4:54 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Mon Dec 11, 5:14 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Fri Dec 15, 2:45 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Fri Dec 15, 3:20 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Fri Dec 15, 4:41 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Fri Dec 15, 5:04 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Linus Torvalds, (Mon Dec 11, 3:25 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Alex Riesen, (Mon Dec 11, 6:00 am)
Re: [RFC \ WISH] Add -o option to git-rev-list, Marco Costalba, (Sun Dec 10, 6:09 pm)
globs in partial checkout?, Michael S. Tsirkin, (Sun Dec 10, 4:00 pm)
Re: globs in partial checkout?, Linus Torvalds, (Sun Dec 10, 4:13 pm)
Re: globs in partial checkout?, Michael S. Tsirkin, (Sun Dec 10, 5:07 pm)
Re: [RFC \ WISH] Add -o option to git-rev-list, Alex Riesen, (Sun Dec 10, 10:54 am)