Residency profiles

[Sebastian Graf]

This recently came up again. It seems that `+RTS -h -i0` will just turn
every minor collection into a major one:
https://gitlab.haskell.org/ghc/ghc/issues/17387#note_248705
`-i0` seems significantly different from `-i0.001`, say, in that it just
turns minor GCs into major ones and doesn't introduce non-determinism
otherwise. Sampling rate can be controlled with `-A`, much like `-F1` (but
it's still faster for some reason).

Am Mo., 10. Dez. 2018 um 09:11 Uhr schrieb Simon Marlow <marlowsd at gmail.com
>:

> https://phabricator.haskell.org/D5428
>
>
> On Sun, 9 Dec 2018 at 10:12, Sebastian Graf <sgraf1337 at gmail.com> wrote:
>
>> Ah, I was only looking at `+RTS --help`, not the users guide. Silly me.
>>
>> Am Do., 6. Dez. 2018 um 20:53 Uhr schrieb Simon Marlow <
>> marlowsd at gmail.com>:
>>
>>> It is documented!
>>> https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/runtime_control.html#rts-flag--F%20%E2%9F%A8factor%E2%9F%A9
>>>
>>> On Thu, 6 Dec 2018 at 16:21, Sebastian Graf <sgraf1337 at gmail.com> wrote:
>>>
>>>> Hey,
>>>>
>>>> thanks, all! Measuring with `-A1M -F1` delivers much more reliable
>>>> residency numbers.
>>>> `-F` doesn't seem to be documented. From reading `rts/RtsFlags.c` and
>>>> `rts/sm/GC.c` I gather that it's the factor by which to multiply the number
>>>> of live bytes by to get the new old gen size?
>>>> So effectively, the old gen will 'overflow' on every minor GC, neat!
>>>>
>>>> Greetings
>>>> Sebastian
>>>>
>>>> Am Do., 6. Dez. 2018 um 12:52 Uhr schrieb Simon Peyton Jones via
>>>> ghc-devs <ghc-devs at haskell.org>:
>>>>
>>>>> |  Right. A parameter for fixing the nursery size would be easy to
>>>>> implement,
>>>>> |  I think. Just a new flag, then in GC.c:resize_nursery() use the
>>>>> flag as the
>>>>> |  nursery size.
>>>>>
>>>>> Super!  That would be v useful.
>>>>>
>>>>> |  "Max. residency" is really hard to measure (need to do very
>>>>> frequent GCs),
>>>>> |  perhaps a better question to ask is "residency when the program is
>>>>> in state
>>>>> |  S".
>>>>>
>>>>> Actually, Sebastian simply wants to see an accurate, reproducible
>>>>> residency profile, and doing frequent GCs might well be an acceptable
>>>>> cost.
>>>>>
>>>>> Simon
>>>>> _______________________________________________
>>>>> ghc-devs mailing list
>>>>> ghc-devs at haskell.org
>>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>>>>>
>>>>
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