From: Liu Yubao <yubao.liu@gmail.com>
To: "Shawn O. Pearce" <spearce@spearce.org>
Cc: Junio C Hamano <gitster@pobox.com>, git list <git@vger.kernel.org>
Subject: Re: [PATCH 5/5] support writing uncompressed loose object
Date: Wed, 03 Dec 2008 12:22:46 +0800 [thread overview]
Message-ID: <49360996.40106@gmail.com> (raw)
In-Reply-To: <20081202160706.GN23984@spearce.org>
Shawn O. Pearce wrote:
> Liu Yubao <yubao.liu@gmail.com> wrote:
>> Signed-off-by: Liu Yubao <yubao.liu@gmail.com>
>
> IMHO, this needs more description in the commit message.
>
>> diff --git a/sha1_file.c b/sha1_file.c
>> index 05a9fa3..053b564 100644
>> --- a/sha1_file.c
>> +++ b/sha1_file.c
>> @@ -2328,7 +2328,7 @@ static int create_tmpfile(char *buffer, size_t bufsiz, const char *filename)
>> }
>>
>> static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
>> - void *buf, unsigned long len, time_t mtime)
>> + void *buf, unsigned long len, time_t mtime, int dont_deflate)
>
> Passing this as an argument is pointless. It should be a repository
> wide configuration option in core, so you can declare it a static and
> allow git_config to populate it. Defaulting to 1 (no compression)
> like you do elsewhere in the patch isn't good.
>
Aha, sorry again, I sent the patch series as separate topics by mistake.
I considered adding a configuration variable, the patch series are sent
just to see whether the idea is worth.
> I'm still against this file format change. The series itself isn't
> that bad, and the buffer overflow catch in parse_sha1_header()
> may be something worthwhile fixing. But I'm still not sold that
> introducing a new loose object format is worth it.
>
> I'd rather use a binary header encoding like the new-style/in-pack
> format rather than the older style text headers. Its faster to
> parse for one thing.
>
The key point I suggest is to use *uncompressed* loose object, I didn't
change the format of uncompressed loose object because I don't want
to distract your attention and keep the patches small.
> Your changes in the reading code cause a copy of the buffer we
> mmap()'d. That sort of ruins your argument that this change is
> worthwhile because concurrent processes on the same host can mmap the
> same buffer and save memory. We're still copying the buffer anyway.
> I probably should have commented on that in patch 4/5, but I just
> realized it, so I'm saying it here.
>
Yes, I mentioned it in the cover letter(sigh, sorry!)
I didn't use the mapped buffer directly because other functions required
a null terminated buffer to parse data part of loose object. It can be
fixed but I don't want to make the patches too big.
The two big pros of uncompressed loose object are:
*) avoid compressing and uncompressing loose objects (I have implemented it)
*) use memory mapped loose object directly (I havn't implemented it)
Thank you for reviewing my patches, seems the idea to use uncompressed loose
object isn't attractive enough, I will keep the patches locally.
Best regards,
Liu Yubao
next prev parent reply other threads:[~2008-12-03 4:24 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-01 8:00 two questions about the format of loose object Liu Yubao
2008-12-01 8:25 ` Junio C Hamano
2008-12-01 9:28 ` Liu Yubao
2008-12-01 11:32 ` Jakub Narebski
2008-12-02 2:19 ` Liu Yubao
2008-12-01 15:21 ` Shawn O. Pearce
2008-12-02 2:43 ` Liu Yubao
2008-12-02 1:48 ` [PATCH 0/5] support reading and writing uncompressed " Liu Yubao
2008-12-02 1:51 ` [PATCH 1/5] avoid parse_sha1_header() accessing memory out of bound Liu Yubao
2008-12-02 15:42 ` Shawn O. Pearce
2008-12-03 3:49 ` Liu Yubao
2008-12-02 1:53 ` [PATCH 2/5] don't die immediately when convert an invalid type name Liu Yubao
2008-12-02 1:55 ` [PATCH 3/5] optimize parse_sha1_header() a little by detecting object type Liu Yubao
2008-12-02 15:53 ` Shawn O. Pearce
2008-12-03 4:06 ` Liu Yubao
2008-12-02 1:56 ` [PATCH 4/5] support reading uncompressed loose object Liu Yubao
2008-12-02 15:58 ` Shawn O. Pearce
2008-12-03 4:09 ` Liu Yubao
2008-12-02 2:03 ` [PATCH 5/5] support writing " Liu Yubao
2008-12-02 16:07 ` Shawn O. Pearce
2008-12-03 4:22 ` Liu Yubao [this message]
2008-12-02 3:11 ` [PATCH 0/5] support reading and " Liu Yubao
2008-12-01 12:16 ` two questions about the format of " Nick Andrew
2008-12-02 2:26 ` Liu Yubao
2008-12-01 15:32 ` Shawn O. Pearce
2008-12-02 3:05 ` Liu Yubao
2008-12-04 0:54 ` Nicolas Pitre
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