Messages in this thread | | | Date | Fri, 19 Feb 2016 10:19:57 +0900 | Subject | Re: [RFC PATCH 3/3] mm/zsmalloc: change ZS_MAX_PAGES_PER_ZSPAGE | From | Joonsoo Kim <> |
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2016-02-18 19:19 GMT+09:00 Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>: > On (02/18/16 18:55), Sergey Senozhatsky wrote: >> > There is a reason that it is order of 2. Increasing ZS_MAX_PAGES_PER_ZSPAGE >> > is related to ZS_MIN_ALLOC_SIZE. If we don't have enough OBJ_INDEX_BITS, >> > ZS_MIN_ALLOC_SIZE would be increase and it causes regression on some >> > system. >> >> Thanks! >> >> do you mean PHYSMEM_BITS != BITS_PER_LONG systems? PAE/LPAE? isn't it >> the case that on those systems ZS_MIN_ALLOC_SIZE already bigger than 32?
Indeed.
> I mean, yes, there are ZS_ALIGN requirements that I completely ignored, > thanks for pointing that out. > > just saying, not insisting on anything, theoretically, trading 32 bit size > objects in exchange of reducing a much bigger memory wastage is sort of > interesting. zram stores objects bigger than 3072 as huge objects, leaving
I'm also just saying. :) On the above example system which already uses 128 byte min class, your change makes it to 160 or 192. It could make a more trouble than you thought.
> 4096-3072 bytes unused, and it'll take 4096-3072/32 = 4000 32 bit objects > to beat that single 'bad' compression object in storing inefficiency...
Where does 4096-3072/32 calculation comes from? I'm not familiar to recent change on zsmalloc such as huge class so can't understand this calculation.
> well, patches 0001/0002 are trying to address this a bit, but the biggest > problem is still there: we have too many ->huge classes and they are a bit > far from good.
Agreed. And I agree your patchset, too.
Anyway, could you answer my other questions on original reply?
Thanks.
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