Thanks a lot Dormando.
We have made some customization to the code and we are using ITEM_data
macro in order to retrieve the value of the key.
This work for all slabs except the last one. Is there any way to
programmatically retrieve the data ?
Thanks,
Bob.
On Tuesday, June 6, 2023 at 11:22:44 PM UTC+3 dormando wrote:
> Hey,
>
> Items larger than the slab class max are "chunked" across multiple slab
> chunks. See: https://github.com/memcached/memcached/wiki/ReleaseNotes1429
>
> Since that release a "cap" chunk mode was added, so if chunk max is set to
> 16k and you store a 17k item, it will split into:
>
> 1) tiny chunk for key and header
> 2) 16k main chunk
> 3) attempt to "cap" with a 1k chunk
>
> if it cannot allocate the 1k cap memory for some reason it will allocate
> an extra 16k chunk instead.
>
> The theory is that at larger item sizes we can spend a little CPU to
> improve the memory efficiency. Making the "max slab class" smaller means
> we can make better use of the slab classes. At some point I will be
> reducing the default setting from 512k to 256k or lower, but I need to
> revisit it and add some stats counters first.
>
> -Dormando
>
> On Tue, 6 Jun 2023, boaz shavit wrote:
>
> > Hello,I'm trying to understand how data is saved in memcached for items
> with size > 0.5M.
> > When I check the slabclass structure array, I see it only has values for
> classes up to .5 MB and another entry in place zero which looks like this:
> > (gdb) p slabclass[0]
> > $87 = {size = 0, perslab = 0, slots = 0x0, sl_curr = 0, slabs = 386,
> slab_list = 0x7f15b4015ef0, list_size = 2048}
> >
> > when inserting a value which is very big (the key is 100 bytes, but the
> value is 800k) I see that the key goes to class 2 (which is 196 bytes) but
> I do
> > not see where the value is stored.
> >
> > Can someone explain how this works for big values?
> >
> > Thanks in advanced,
> > Bob.
> >
> > --
> >
> > ---
> > 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 memcached+...@googlegroups.com.
> > To view this discussion on the web visit
> https://groups.google.com/d/msgid/memcached/dedecb91-b3d2-4a83-8253-0ad965cecd68n%40googlegroups.com
> .
> >
> >
--
---
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 memcached+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/memcached/e2254937-3369-4cc2-9de5-6982d1ef9066n%40googlegroups.com.
