I don't really understand what queue tail is. I didn't write that page. There's the LRU tail. Which just means the least recently used item for that slab class.
On Tue, 20 Jun 2017, red 888 wrote: > Just curious about what the queue tail is and where I can get more info about > it and what it does. > > On Jun 20, 2017 5:25 PM, "dormando" <[email protected]> wrote: > On Tue, 20 Jun 2017, red 888 wrote: > > > This doc says something about memcached I haven't read anywhere else: > > Which brings me to another point, items/chunks are not actively > reclaimed/expired. > Memached does not > > have a background thread that explicitly expires items, reclaiming > used chunks for new > items. When a > > slab needs a chunk and there are no more pages, Memcache will look at > the queue tail > for items to > > evict. Memcache will make a best effort to evict expired items (items > you've explicitly > set to expire > > after some time). In scenario 1, item 2, an expired item, is evicted. > However, in > scenario 2, item 1, > > which has not yet expired, will be evicted, even though item 4 would > seem like the > better candidate. > > But since item 4 is not near the tail, Memcached stops looking and > just expires item 1. > > > > So what is the memcache queue tail and why can't I find much info > about it? Seems > pretty important > > because what he is saying is that memcache could evict a non expired > item, if it ran > out of > > unassigned pages, had plenty of expire items for the slab classes, > but because an > expired was nearer > > the "tail" (whatever that means) it evicted that one instead. > > What is the problem you're trying to solve? > > If you run the latest version and start it with "-o modern" option, > there's an LRU crawler that will reap expired items in the background. > > -- > > --- > You received this message because you are subscribed to a topic in the > Google Groups > "memcached" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/memcached/liqaRhhYi3A/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- > > --- > You received this message because you are subscribed to the Google Groups > "memcached" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > > -- --- You received this message because you are subscribed to the Google Groups "memcached" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
