> > Some my own previous thoughts about this strategy: > > - If we allocate all memory and map these before I/Os, all inflight I/Os > will keep such temporary pages all the time until decompression is > finished. In contrast, if we allocate or reuse such pages just before > decompression, it would minimize the memory footprints. > > I think it will impact the memory numbers at least on the very > low-ended devices with bslow storage. (I've seen f2fs has some big > mempool already) > > - Many compression algorithms are not suitable in the softirq contexts, > also I vaguely remembered if softirq context lasts for > 2ms, it will > push into ksoftirqd instead so it's actually another process context. > And it may delay other important interrupt handling. > > - Go back to the non-deterministic scheduling of workqueues. I guess it > may be just due to scheduling punishment due to a lot of CPU consuming > due to decompression before so the priority becomes low, but that is > just a pure guess. May be we need to use RT scheduling policy instead. > > At least with WQ_HIGHPRI for dm-verity at least, but I don't find > WQ_HIGHPRI mark for dm-verity. > > Thanks, > Gao Xiang
I totally understand what you are worried about. However, in the real world, non-determinism from workqueues is more harsh than we expected. As you know, reading I/Os in the system are critical paths most of the time and now I/O variations with workqueue are too bad. I also think it's better that we have RT scheduling like things here. We could think about it more. Thanks, _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
