RFC We keep compression work memory buffer per-comp stream (which is per-CPU), but we don't need that many buffers, because on each CPU only one compression backend can access work memory at any given time. Hence the patch series moves compression work memory to a dedicated per-CPU area, reducing the amount of memory we allocate for those buffers. For instance, assume a 12 CPUs system, 2 compression streams per-CPU (a default and one for deferred recompression). Before we'd allocate 12 * 2 * 2 pages, after we'll allocate 12 * 2 pages. NOTE: The series stops short of moving comp buffers to a global per-CPU area, which all zram devices can share. Compression backends use CPUs exclusively (disable migration and CPU hotplug), so in theory comp work memory can be in global per-CPU data. This can reduce memory usage on systems that init numerous zram devices. E.g. instead of num-zram-devices * num-cpus buffers we'll allocate only num-cpus buffers. Sergey Senozhatsky (2): zram: do not allocate buffer if crypto comp allocation failed zram: move comp buffer to a dedicate per-CPU area drivers/block/zram/zcomp.c | 118 +++++++++++++++++++++++++++++----- drivers/block/zram/zcomp.h | 24 +++++-- drivers/block/zram/zram_drv.c | 32 +++++++-- drivers/block/zram/zram_drv.h | 1 + include/linux/cpuhotplug.h | 1 + 5 files changed, 151 insertions(+), 25 deletions(-) -- 2.43.0.594.gd9cf4e227d-goog
