On Tue, Nov 20, 2018 at 11:46:59AM +0900, Sergey Senozhatsky wrote: > Hello, > > On (11/16/18 16:20), Minchan Kim wrote: > [..] > > +static ssize_t idle_store(struct device *dev, > > + struct device_attribute *attr, const char *buf, size_t len) > > +{ > > + struct zram *zram = dev_to_zram(dev); > > + unsigned long nr_pages = zram->disksize >> PAGE_SHIFT; > > + int index; > > + > > + down_read(&zram->init_lock); > > + if (!init_done(zram)) { > > + up_read(&zram->init_lock); > > + return -EINVAL; > > + } > > + > > + for (index = 0; index < nr_pages; index++) { > > + zram_slot_lock(zram, index); > > + if (!zram_allocated(zram, index)) > > + goto next; > > + > > + zram_set_flag(zram, index, ZRAM_IDLE); > > +next: > > + zram_slot_unlock(zram, index); > > + } > > + > > + up_read(&zram->init_lock); > > + > > + return len; > > +} > > This is one way of doing it. > > The other one could, probabaly, be a bit more friendly to the cache > lines and CPU cycles. Basically, have a static timestamp variable, > which would keep the timestamp of last idle_store(). > > static idle_snapshot_ts; > > static ssize_t idle_store(struct device *dev, > struct device_attribute *attr, > const char *buf, size_t len) > { > idle_snapshot_ts = ktime(); > } > > And then in read_block_state() compare handle access time and > idle_snapshot_ts (if it's not 0). If the page was not modified/access > since the last idle_snapshot_ts (handle access time <= idle_snapshot_ts), > then it's idle, otherwise (handle access time > idle_snapshot_ts) it's > not idle. > > Would this do the trick?
It was a option when I imagined this idea first but problem from product division was memory waste of ac_time for every zram table.