Re: [PATCH v6 09/13] zram: split zcomp into separate R/W streams

[Sergey Senozhatsky]

On (26/10/21 12:23), Hillf Danton wrote:
> On Wed, 21 Oct 2026 11:42:19 +0900 Sergey Senozhatsky wrote:
> > Split struct zcomp_strm into separate compression (Write zcomp_cstrm)
> > and decompression (Read zcomp_dstrm) streams, and split zcomp_ops
> > context creation/destruction into create_cctx/destroy_cctx and
> > optional create_dctx/destroy_dctx callbacks.
> > 
> > This decouples Read (decompression) and Write (compression) paths so
> > they no longer contend on the same per-CPU stream mutex (Writer vs
> > Reader priority inversion).  Currently, a (low priority) Writer that
> > holds the stream mutex can be preempted by a (higher priority) Reader
> > on the same CPU, which then blocks on that mutex until the Writer gets
> > to run again and releases it, which can take a long time when there
> > are other runnable tasks on that CPU.
> >
> Given lock like mutex, priority inversion happens from Monday to Friday,
> but I wonder if you are inventing some wheels in 2026 if proxy excution
> works for you.

Reader-Writer split is a foundation for further improvements (like
singleton recompression stream and so on).