Re: Some rough edges of core.fsmonitor

> While the hook itself takes ~20ms (and watchman itself 1/4 of that)
> status as a whole takes much longer. gprof reveals:
>
>     Each sample counts as 0.01 seconds.
>       %   cumulative   self              self     total
>      time   seconds   seconds    calls  ms/call  ms/call  name
>      15.38      0.02     0.02   221690     0.00     0.00  memihash

>      15.38      0.04     0.02   221689     0.00     0.00  create_from_disk
>       7.69      0.05     0.01  2216897     0.00     0.00  git_bswap32
>       7.69      0.06     0.01   222661     0.00     0.00  ce_path_match
>       7.69      0.07     0.01   221769     0.00     0.00  hashmap_add
>       7.69      0.08     0.01    39941     0.00     0.00  prep_exclude
>       7.69      0.09     0.01    39940     0.00     0.00  strbuf_addch
>       7.69      0.10     0.01        1    10.00    10.00  read_one
>       7.69      0.11     0.01        1    10.00    10.00  refresh_index
>       7.69      0.12     0.01        1    10.00    10.00  tweak_fsmonitor
>       7.69      0.13     0.01                             preload_thread
>
> The index is 24M in this case, I guess it's unpacking it, but I wonder
> if this couldn't be much faster if we saved away the result of the last
> "status" in something that's quick to access, and then if nothing