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Lot of misses

Posted by marrra 
marrra
Lot of misses
August 18, 2010 10:00AM
Hi,

I'm using memcached for caching search suggest box.

I've done this:
Set lifetime for all items to 30 hours and restart memcached.
After 24hours are stored about 87000 items in memcached and in last 2
hours was added only few items.
When I look at graf (bijk.com) I see cache hits and misses are almost
equal now.

Why? I think that now would by almost only hits.

Here is stats:
STAT pid 13863
STAT uptime 88895
STAT time 1282116614
STAT version 1.2.2
STAT pointer_size 64
STAT rusage_user 12.132758
STAT rusage_system 32.578036
STAT curr_items 87184
STAT total_items 176452
STAT bytes 56215815
STAT curr_connections 2
STAT total_connections 385143
STAT connection_structures 48
STAT cmd_get 385139
STAT cmd_set 176452
STAT get_hits 229838
STAT get_misses 155301
STAT evictions 67890
STAT bytes_read 90153265
STAT bytes_written 522373778
STAT limit_maxbytes 67108864
STAT threads 1
Matt Ingenthron
Re: Lot of misses
August 18, 2010 06:42PM
marrra wrote:
> Hi,
>
> I'm using memcached for caching search suggest box.
>
> I've done this:
> Set lifetime for all items to 30 hours and restart memcached.
> After 24hours are stored about 87000 items in memcached and in last 2
> hours was added only few items.
> When I look at graf (bijk.com) I see cache hits and misses are almost
> equal now.
>

Did you notice your evictions?

> Why? I think that now would by almost only hits.
>
> Here is stats:
> STAT pid 13863
> STAT uptime 88895
> STAT time 1282116614
> STAT version 1.2.2
> STAT pointer_size 64
> STAT rusage_user 12.132758
> STAT rusage_system 32.578036
> STAT curr_items 87184
> STAT total_items 176452
> STAT bytes 56215815
> STAT curr_connections 2
> STAT total_connections 385143
> STAT connection_structures 48
> STAT cmd_get 385139
> STAT cmd_set 176452
> STAT get_hits 229838
> STAT get_misses 155301
> STAT evictions 67890
> STAT bytes_read 90153265
> STAT bytes_written 522373778
> STAT limit_maxbytes 67108864
> STAT threads 1
>
marrra
Re: Lot of misses
August 18, 2010 08:10PM
I am new to memcached.

if i understand it well, evictions menas memcached is out memory ?

I've changed memory to 256MB.
I hope it will work.

Thank you.
Best regards.

On Aug 18, 6:41 pm, Matt Ingenthron <[email protected]> wrote:
> marrra wrote:
> > Hi,
>
> > I'm using memcached for caching search suggest box.
>
> > I've done this:
> > Set lifetime for all items to 30 hours and restart memcached.
> > After 24hours are stored about 87000 items in memcached and in last 2
> > hours was added only few items.
> > When I look at graf (bijk.com) I see cache hits and misses are almost
> > equal now.
>
> Did you notice your evictions?
>
> > Why? I think that now would by almost only hits.
>
> > Here is stats:
> > STAT pid 13863
> > STAT uptime 88895
> > STAT time 1282116614
> > STAT version 1.2.2
> > STAT pointer_size 64
> > STAT rusage_user 12.132758
> > STAT rusage_system 32.578036
> > STAT curr_items 87184
> > STAT total_items 176452
> > STAT bytes 56215815
> > STAT curr_connections 2
> > STAT total_connections 385143
> > STAT connection_structures 48
> > STAT cmd_get 385139
> > STAT cmd_set 176452
> > STAT get_hits 229838
> > STAT get_misses 155301
> > STAT evictions 67890
> > STAT bytes_read 90153265
> > STAT bytes_written 522373778
> > STAT limit_maxbytes 67108864
> > STAT threads 1
Matt Ingenthron
Re: Lot of misses
August 18, 2010 09:22PM
marrra wrote:
> I am new to memcached.
>
> if i understand it well, evictions menas memcached is out memory ?
>

Yes. memcached is an LRU(ish) cache. Therefore, when you go beyond the
memory available, it'll find an old item to evict to store the new item
you're asking it to store.

Since you're new, I'd highly recommend looking at this:
http://code.google.com/p/memcached/wiki/NewServerMaint

> I've changed memory to 256MB.
> I hope it will work.
>

Chances are this will lower your evictions, and you'll have more hits.

There are a few other things that could be done to make it more
efficient, but the first step it seems in your case would be to add more
memory. Since you've done that, I bet it'll help.

- Matt
>
> On Aug 18, 6:41 pm, Matt Ingenthron <[email protected]> wrote:
>
>> marrra wrote:
>>
>>> Hi,
>>>
>>> I'm using memcached for caching search suggest box.
>>>
>>> I've done this:
>>> Set lifetime for all items to 30 hours and restart memcached.
>>> After 24hours are stored about 87000 items in memcached and in last 2
>>> hours was added only few items.
>>> When I look at graf (bijk.com) I see cache hits and misses are almost
>>> equal now.
>>>
>> Did you notice your evictions?
>>
>>
>>> Why? I think that now would by almost only hits.
>>>
>>> Here is stats:
>>> STAT pid 13863
>>> STAT uptime 88895
>>> STAT time 1282116614
>>> STAT version 1.2.2
>>> STAT pointer_size 64
>>> STAT rusage_user 12.132758
>>> STAT rusage_system 32.578036
>>> STAT curr_items 87184
>>> STAT total_items 176452
>>> STAT bytes 56215815
>>> STAT curr_connections 2
>>> STAT total_connections 385143
>>> STAT connection_structures 48
>>> STAT cmd_get 385139
>>> STAT cmd_set 176452
>>> STAT get_hits 229838
>>> STAT get_misses 155301
>>> STAT evictions 67890
>>> STAT bytes_read 90153265
>>> STAT bytes_written 522373778
>>> STAT limit_maxbytes 67108864
>>> STAT threads 1
>>>
marrra
Re: Lot of misses
August 20, 2010 04:50PM
Thank you, now it works.
There aren't evictations.

I've find out that I've lot of unique search..

On Aug 18, 9:18 pm, Matt Ingenthron <[email protected]> wrote:
> marrra wrote:
> > I am new to memcached.
>
> > if i understand it well, evictions menas memcached is out memory ?
>
> Yes.  memcached is an LRU(ish) cache.  Therefore, when you go beyond the
> memory available, it'll find an old item to evict to store the new item
> you're asking it to store.
>
> Since you're new, I'd highly recommend looking at this:http://code.google..com/p/memcached/wiki/NewServerMaint
>
> > I've changed memory to 256MB.
> > I hope it will work.
>
> Chances are this will lower your evictions, and you'll have more hits.
>
> There are a few other things that could be done to make it more
> efficient, but the first step it seems in your case would be to add more
> memory.  Since you've done that, I bet it'll help.
>
> - Matt
>
>
>
>
>
> > On Aug 18, 6:41 pm, Matt Ingenthron <[email protected]> wrote:
>
> >> marrra wrote:
>
> >>> Hi,
>
> >>> I'm using memcached for caching search suggest box.
>
> >>> I've done this:
> >>> Set lifetime for all items to 30 hours and restart memcached.
> >>> After 24hours are stored about 87000 items in memcached and in last 2
> >>> hours was added only few items.
> >>> When I look at graf (bijk.com) I see cache hits and misses are almost
> >>> equal now.
>
> >> Did you notice your evictions?
>
> >>> Why? I think that now would by almost only hits.
>
> >>> Here is stats:
> >>> STAT pid 13863
> >>> STAT uptime 88895
> >>> STAT time 1282116614
> >>> STAT version 1.2.2
> >>> STAT pointer_size 64
> >>> STAT rusage_user 12.132758
> >>> STAT rusage_system 32.578036
> >>> STAT curr_items 87184
> >>> STAT total_items 176452
> >>> STAT bytes 56215815
> >>> STAT curr_connections 2
> >>> STAT total_connections 385143
> >>> STAT connection_structures 48
> >>> STAT cmd_get 385139
> >>> STAT cmd_set 176452
> >>> STAT get_hits 229838
> >>> STAT get_misses 155301
> >>> STAT evictions 67890
> >>> STAT bytes_read 90153265
> >>> STAT bytes_written 522373778
> >>> STAT limit_maxbytes 67108864
> >>> STAT threads 1
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