Messages in this thread | | | Date | Thu, 18 Jun 2015 12:46:50 +0900 | From | Minchan Kim <> | Subject | Re: [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction |
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On Thu, Jun 18, 2015 at 12:01:36PM +0900, Sergey Senozhatsky wrote: > On (06/18/15 11:41), Sergey Senozhatsky wrote: > [..] > > > My concern is not a compacion overhead but higher memory footprint > > > consumed by zram in reserved memory. > > > It might hang system if zram used up reserved memory of system with > > > ALLOC_NO_WATERMARKS. With auto-compaction, userspace has a higher chance > > > to use more memory with uncompressible pages or file-backed pages > > > so zram-swap can use more reserved memory. We need to evaluate it, I think. > > > > > a couple of _not really related_ ideas that I want to voice. > > (a) I'm thinking of extending zramX/compact attr. right now it's WO, > and I think it makes sense to make it RW: > ->write will trigger compaction > ->read will return estimated number of bytes > "zs_can_compact() * pages per zspage * page_size" that can be freed. > so user-space will have at least minimal idea whether compaction is > reasonable. but sure, this is racy and in general case things may > change between `cat compact` and `echo 1 > compact`.
It's a good idea. with that, memory manager on platform could be smart.
if memory pressure == soft and zram.can_compact > 20M do zram.compact if memory pressure == hard and zram.can_compact > 5M do zram.compact
With this, userspace have more flexibility. :)
However, FYI, I want to make auto-compact default in future so let's see how auto-compact is going.
> > > (b) adding a knob (yeah, like we don't have enough knobs already :-)) > that will allow 'enable/disable auto compaction'.
I agree.
> > -ss
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