RFR (S): 8155229: Tune thread usage for live data clearing
derek.white at oracle.com
Thu Apr 28 19:14:46 UTC 2016
On 4/28/16 10:28 AM, Mikael Gerdin wrote:
> Hi Thomas,
> On 2016-04-28 13:16, Thomas Schatzl wrote:
>> Hi all,
>> during testing of 8077144 I found that live bitmap clear can be
>> significantly sped up by not using that many threads.
>> A good conservative estimate (tends to use too many threads) that still
>> cuts mark bitmap clear time by >50% is to give each thread at least 1
>> MB of data to clear.
> The fix looks good.
> One thing though,
> now that I think about it, would it make sense to add an additional
> logging tag to
> + log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT
> " work units.", cl.name(), num_workers, num_chunks);
> Since these logging statements are not really about GC ergonomics but
> rather GC worker ergonomics.
> This can be fixed further on too, I just want to hear if anyone else
> gets the same feeling.
I have a slight preference for leaving as-is. From my (very) little
experience with UL, I think keeping the tag set small is more helpful
than a having a huge number of specific tags.
>> jprt, webrev, various performance tests
>> Depends on 8155232.
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