On 5/16/23 2:41 PM, Chaitanya Kulkarni wrote: > On 5/16/23 06:08, Sergey Senozhatsky wrote: >> On (23/05/16 05:51), Chaitanya Kulkarni wrote: >>> Removed modparam v2 is ready to send, but I've few concerns enabling >>> nowait unconditionally for zram :- >>> >>> From brd data [1] and zram data [2] from my setup :- >>> >>> IOPs (old->new) | sys cpu% (old->new) >>> -------------------------------------------------- >>> brd | 1.5x (3919 -> 5874) | 3x (29 -> 87) >>> zram | 1.09x ( 29 -> 87) | 9x (11 -> 97) >>> >>> brd:- >>> IOPs increased by ~1.5 times (50% up) >>> sys CPU percentage increased by ~3.0 times (200% up) >>> >>> zram:- >>> IOPs increased by ~1.09 times ( 9% up) >>> sys CPU percentage increased by ~8.81 times (781% up) >>> >>> This comparison clearly demonstrates that zram experiences a much more >>> substantial CPU load relative to the increase in IOPs compared to brd. >>> Such a significant difference might suggest a potential CPU regression >>> in zram ? >>> >>> Especially for zram, if applications are not expecting this high cpu >>> usage then they we'll get regression reports with default nowait >>> approach. How about we avoid something like this with one of the >>> following options ? >> Well, zram performs decompression/compression on the CPU (per-CPU >> crypto streams) for each IO operation, so zram IO is CPU intensive. > > and that is exactly I've raised this issue, are you okay with that ? > I'll send V2 with nowait enabled by default .. Did you check that it's actually nowait sane to begin with? I spent literally 30 seconds on that when you sent the first patch, and the partial/sync path does not look kosher. -- Jens Axboe
