RE: [External Mail]Re: Partial-clone cause big performance impact on server

But I still think the protocol still should tell the server which ref the blob is reachable.
Because it would be really hard to implement any kind of ACL
But git is surely designed for open sources community. It makes senses this request will be rejected.

-----Original Message-----
From: Derrick Stolee <redacted>
Sent: Monday, August 15, 2022 9:19 PM
To: Jeff King <redacted>; 程洋 <redacted>
Cc: git@vger.kernel.org; 何浩 <redacted>; Xin7 Ma 马鑫
[off-list ref]; 石奉兵 [off-list ref]; 凡军辉
[off-list ref]; 王汉基 [off-list ref]
Subject: [External Mail]Re: Partial-clone cause big performance impact on
server

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On 8/14/2022 2:48 AM, Jeff King wrote:

quoted

On Thu, Aug 11, 2022 at 08:09:56AM +0000, 程洋 wrote:

quoted

    4. And we then track our server(which is gerrit with jgit). We
       found the server is couting objects. Then we check those 40k
       objects, most of them are blobs rather than commit. (which
       means they're not in bitmap)
    5. We believe that's the root cause of our problem. Git sends too
       many "want SHA1" which are not in bitmap, cause the server to
       count objects  frequently, which then slow down the server.

I'd be surprised if bitmaps make a big difference either way here,
since blobs are very quick in the "counting" phase of pack-objects.
They can't link to anything else, so we should not be opening the
object contents at all! We just need to find them on disk, and then in
many cases we can send them over the wire without even decompressing
(the exception is if they are stored as deltas against an object the client

doesn't have).

quoted

I didn't generate a test case, but I'm pretty sure that is how
git.git's pack-objects should behave. But you mentioned that the
server is jgit; it's possible that it isn't as optimized in that area.

I just remembered that Gerrit specifically has branch-level security, where
some branches are not visible to all users. For that reason, blobs cannot be
served without first determining if they are reachable from a branch visible
to the current user.

I'm not sure if that's the problem in this particular case, but it could be.

Thanks,
-Stolee

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