Hello Minchan, sorry for very long reply. On (02/24/16 01:05), Minchan Kim wrote: [..] > > And the thing is -- quite huge internal class fragmentation. These are the 'normal' > > classes, not affected by ORDER modification in any way: > > > > class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage compact > > 107 1744 1 23 196 76 84 3 51 > > 111 1808 0 0 63 63 28 4 0 > > 126 2048 0 160 568 408 284 1 80 > > 144 2336 52 620 8631 5747 4932 4 1648 > > 151 2448 123 406 10090 8736 6054 3 810 > > 168 2720 0 512 15738 14926 10492 2 540 > > 190 3072 0 2 136 130 102 3 3 > > > > > > so I've been thinking about using some sort of watermaks (well, zsmalloc is an allocator > > after all, allocators love watermarks :-)). we can't defeat this fragmentation, we never > > know in advance which of the pages will be modified or we the size class those pages will > > land after compression. but we know stats for every class -- zs_can_compact(), > > obj_allocated/obj_used, etc. so we can start class compaction if we detect that internal > > fragmentation is too high (e.g. 30+% of class pages can be compacted). > > AFAIRC, we discussed about that when I introduced compaction. > Namely, per-class compaction. > I love it and just wanted to do after soft landing of compaction. > So, it's good time to introduce it. ;-) ah, yeah, indeed. I vaguely recall this. my first 'auto-compaction' submission has had this "compact every class in zs_free()", which was a subject to 10+% performance penalty on some of the tests. but with watermarks this will be less dramatic, I think. > > > > on the other hand, we always can wait for the shrinker to come in and do the job for us, > > but that can take some time. > > Sure, with the feature, we can remove shrinker itself, I think. > > > > what's your opinion on this? > > I will be very happy. good, I'll take a look later, to avoid any conflicts with your re-work. [..] > > does it look to you good enough to be committed on its own (off the series)? > > I think it's good to have. Firstly, I thought we can get the information > by existing stats with simple math on userspace but changed my mind > because we could change the implementation sometime so such simple math > might not be perfect in future and even, we can expose it easily so yes, > let's do it. thanks! submitted. -ss -- 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>