Re: [RFC] pack-objects: compression level for non-blobs

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Dec 29, 2012, 05:25 UTC
Message-ID: <CACsJy8AN3y_4wcZ_w0zz+ZAaDasRT-+h8vA_fp2j4+FL00dbLw@mail.gmail.com>
In-Reply-To: <20121229050707.GA14475@sigill.intra.peff.net>

On Sat, Dec 29, 2012 at 12:07 PM, Jeff King <peff@peff.net> wrote:

Show 15 quoted lines

> On Sat, Dec 29, 2012 at 11:34:09AM +0700, Nguyen Thai Ngoc Duy wrote:
>
>> On Sat, Dec 29, 2012 at 7:41 AM, Jeff King <peff@peff.net> wrote:
>> > I wonder if we could do even better, though. For a traversal, we only
>> > need to look at the commit header. We could potentially do a progressive
>> > inflate and stop before getting to the commit message (which is the bulk
>> > of the data, and the part that is most likely to benefit from
>> > compression).
>>
>> Commit cache should solve this efficiently as it also eliminates
>> parsing cost. We discussed this last time as a side topic of the
>> reachability bitmap feature.
>
> I agree that a commit cache would solve this (though it can not help the
> tree traversal).

Yeah, caching trees efficiently is not easy.

> But just dropping the compression (or doing partial
> decompression when we only care about the beginning part) is way less
> code and complexity.

I think I tried the partial decompression for commit header and it did not help much (or I misremember it, not so sure).

> There's no cache to manage.

If reachability bitmap is implemented, we'll have per-pack cache infrastructure ready, so less work there for commit cache.

-- 
Duy