On (24/02/06 19:40), Jens Axboe wrote: > On 2/6/24 6:44 PM, Sergey Senozhatsky wrote: > > On (24/02/07 09:25), Barry Song wrote: > >> From: Barry Song <v-songbaohua@xxxxxxxx> > >> > >> Firstly, there is no need to keep zcomp_strm's buffers contiguous > >> physically. > >> > >> Secondly, The recent mTHP project has provided the possibility to > >> swapout and swapin large folios. Compressing/decompressing large > >> blocks can hugely decrease CPU consumption and improve compression > >> ratio. This requires us to make zRAM support the compression and > >> decompression for large objects. > >> With the support of large objects in zRAM of our out-of-tree code, > >> we have observed many allocation failures during CPU hotplug as > >> large objects need larger buffers. So this change is also more > >> future-proof once we begin to bring up multiple sizes in zRAM. > >> > >> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> > > > > Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx> > > > > Note: > > Taking it in NOT because of the out-of-tree code (we don't really > > do that), but because this is executed from CPU offline/online > > paths, which can happen on devices with fragmented memory (a valid > > concern IMHO). > > > > Minchan, if you have any objections, please chime in. > > Not Minchan, but I do have an issue with the title of the commit, it > doesn't make any sense. Can the maintainer please re-write that to be > something that is appropriate and actually describes what the patch > does? Thanks Jens. I fully agree, I requested a better commit message in v1 feedback, we probably still can improve on this. Something like this? --- zram: do not allocate physically contiguous strm buffers Currently zram allocates 2 physically contigous pages per-CPU's compression stream (we may have up to 3 streams per-CPU). Since those buffers are per-CPU we allocate them from CPU hotplug path, which may have higher risks of failed allocations on devices with fragmented memory. Switch to virtually contiguos allocations - crypto comp does not seem impose requirements on compression working buffers to be physically contiguous.
