2016-03-02 23:09 GMT+09:00 Vlastimil Babka <vbabka@xxxxxxx>: > On 03/02/2016 02:57 PM, Joonsoo Kim wrote: >> >> 2016-03-02 19:04 GMT+09:00 Vlastimil Babka <vbabka@xxxxxxx>: >>> >>> On 03/02/2016 07:33 AM, Joonsoo Kim wrote: >>>> >>>> >>>> >>>> Why you did the test with THP? THP interferes result of main test so >>>> it would be better not to enable it. >>> >>> >>> >>> Hmm I've always left it enabled. It makes for a more realistic >>> interference >>> and would also show unintended regressions in that closely related area. >> >> >> But, it makes review hard because complex analysis is needed to >> understand the result. >> >> Following is the example. >> >> "The compaction stalls >> (direct compaction) in the interfering kernel builds (probably THP's) also >> decreased somewhat to kcompactd activity, yet THP alloc successes improved >> a >> bit." >> >> So, why do we need this comment to understand effect of this patch? If you >> did >> a test without THP, it would not be necessary. > > > I see. Next time I'll do a run with THP disabled. > >>>> And, this patch increased compaction activity (10 times for migrate >>>> scanned) >>>> may be due to resetting skip block information. >>> >>> >>> >>> Note that kswapd compaction activity was completely non-existent for >>> reasons >>> outlined in the changelog. >>>> >>>> Isn't is better to disable it >>>> for this patch to work as similar as possible that kswapd does and >>>> re-enable it >>>> on next patch? If something goes bad, it can simply be reverted. >>>> >>>> Look like it is even not mentioned in the description. >>> >>> >>> >>> Yeah skip block information is discussed in the next patch, which >>> mentions >>> that it's being reset and why. I think it makes more sense, as when >>> kswapd >> >> >> Yes, I know. >> What I'd like to say here is that you need to care current_is_kswapd() in >> this patch. This patch unintentionally change the back ground compaction >> thread >> behaviour to restart compaction by every 64 trials because calling >> curret_is_kswapd() > >> by kcompactd would return false and is treated as direct reclaim. > > Oh, you mean this path to reset the skip bits. I see. But if skip bits are > already reset by kswapd when waking kcompactd, then effect of another (rare) > reset in kcompactd itself will be minimal? If you care current_is_kswapd() in this patch properly (properly means change like "current_is_kcompactd()), reset in kswapd would not happen because, compact_blockskip_flush would not be set by kcompactd. In this case, patch 5 would have it's own meaning so cannot be folded. Thanks. >> Result of patch 4 >> and patch 5 would be same. > > > It's certainly possible to fold patch 5 into 4. I posted them separately > mainly to make review more feasible. But the differences in results are > already quite small. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>