On Tue, Nov 28, 2017 at 6:56 PM, Dmitry Vyukov <dvyu...@google.com> wrote: > On Tue, Nov 28, 2017 at 12:30 PM, Zhouyi Zhou <zhouzho...@gmail.com> wrote: >> Hi, >> By using perf top, qlist_move_cache occupies 100% cpu did really >> happen in my environment yesterday, or I >> won't notice the kasan code. >> Currently I have difficulty to let it reappear because the frontend >> guy modified some user mode code. >> I can repeat again and again now is >> kgdb_breakpoint () at kernel/debug/debug_core.c:1073 >> 1073 wmb(); /* Sync point after breakpoint */ >> (gdb) p quarantine_batch_size >> $1 = 3601946 >> And by instrument code, maximum >> global_quarantine[quarantine_tail].bytes reached is 6618208. > > On second thought, size does not matter too much because there can be > large objects. Quarantine always quantize by objects, we can't part of > an object into one batch, and another part of the object into another > object. But it's not a problem, because overhead per objects is O(1). > We can push a single 4MB object and overflow target size by 4MB and > that will be fine. > Either way, 6MB is not terribly much too. Should take milliseconds to process. > > > > >> I do think drain quarantine right in quarantine_put is a better >> place to drain because cache_free is fine in >> that context. I am willing do it if you think it is convenient :-)
Andrey, do you know of any problems with draining quarantine in push? Do you have any objections? But it's still not completely clear to me what problem we are solving.
