On (24/01/29 10:46), Barry Song wrote: > On Mon, Jan 15, 2024 at 10:35 AM Sergey Senozhatsky > <senozhatsky@xxxxxxxxxxxx> wrote: > > > > On (24/01/06 15:38), Barry Song wrote: > > > On Sat, Jan 6, 2024 at 9:30 AM Sergey Senozhatsky > > > <senozhatsky@xxxxxxxxxxxx> wrote: > > > > > > > > On (24/01/03 13:30), Barry Song wrote: > > > > > There is no need to keep zcomp_strm's buffers contiguous physically. > > > > > And rarely, 1-order allocation can fail while buddy is seriously > > > > > fragmented. > > > > [..] > > Okay, makes sense. > > Do you see these problems in real life? I don't recall any reports. > > i don't have problems with the current zram which supports normal pages only. > > but in our out-of-tree code, we have enhanced zram/zsmalloc to support large > folios compression/decompression, which will make zram work much better > with large anon folios/mTHP things on which Ryan Roberts is working on. > > I mean, a large folio with for example 16 normal pages can be saved as > one object in zram. > In millions of phones, we have deployed this approach and seen huge improvement > on compression ratio and cpu consumption decrease. in that case, we > need a larger > per-cpu buffer, and have seen frequent failure on allocation. that > inspired me to send > this patch in advance. May I please ask you to resend this patch with updated commit mesasge? E.g. mention cpu offlinig/onlining, etc. [..] > > > > I also wonder whether Android uses HW compression, in which case we > > > > may need to have physically contig pages. Not to mention TLB shootdowns > > > > that virt contig pages add to the picture. > > > > > > I don't understand how HW compression and TLB shootdown are related as zRAM > > > is using a traditional comp API. > > > > Oh, those are not related. TLB shootdowns are what now will be added to > > all compressions/decompressions, so it's sort of extra cost. > > i am sorry i still don't understand where the tlb shootdowns come > from. we don't unmap > this per-cpu buffers during compression and decompression, do we ? > > am i missing something? No, I guess you are right.
