https://github.com/memcached/memcached/blob/master/doc/new_lru.txt
On Wed, 21 Jun 2017, red 888 wrote: > Ah thanks that must be what he's talking about. Can you recommend a good in > depth doc on the LRU tail (that includes info about the hot,warm,cold tails)? > Thanks again! > On Tuesday, June 20, 2017 at 8:06:17 PM UTC-4, Dormando wrote: > 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. > > -- --- 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.
