Re: [PATCH v2 0/2] read-cache: call verify_hdr() in a background thread

> From: Jeff Hostetler <jeffhost@microsoft.com>
> 
> Version 2 of this patch series simplifies this to just
> turn off the hash verification.  Independent comments
> from Linus and Peff suggested that we could just turn
> this off and not worry about it.  So I've updated this
> patch to do that.  I added a global variable to allow
> the original code path to be used.  I also added a
> t/helper command to demonstrate the differences.
> 
> On the Linux repo, the effect is rather trivial:
> 
>     $ ~/work/gfw/t/helper/test-skip-verify-index -c 3
>     0.029884 0 [cache_nr 57994]
>     0.031035 0 [cache_nr 57994]
>     0.024308 0 [cache_nr 57994]
>     0.028409 0 avg
>     0.018359 1 [cache_nr 57994]
>     0.017025 1 [cache_nr 57994]
>     0.011087 1 [cache_nr 57994]
>     0.015490 1 avg
> 
> On my Windows source tree (450MB index), I'm seeing a
> savings of 0.6 seconds -- read_index() went from 1.2 to 0.6
> seconds.