Re: [RFC PATCH 0/5] kmalloc-reclaimable caches

[Matthew Wilcox]

On Thu, May 24, 2018 at 01:00:06PM +0200, Vlastimil Babka wrote:
> Now for the issues a.k.a. why RFC:
> 
> - I haven't find any other obvious users for reclaimable kmalloc (yet)

Is that a problem?  This sounds like it's enough to solve Facebook's
problem.

> - the name of caches kmalloc-reclaimable-X is rather long

Yes; Christoph and I were talking about restricting slab names to 16 bytes
just to make /proc/slabinfo easier to read.  How about

kmalloc-rec-128k
1234567890123456

Just makes it ;-)

Of course, somebody needs to do the work to use k/M instead of 4194304.
We also need to bikeshed about when to switch; should it be:

kmalloc-rec-512
kmalloc-rec-1024
kmalloc-rec-2048
kmalloc-rec-4096
kmalloc-rec-8192
kmalloc-rec-16k

or should it be

kmalloc-rec-512
kmalloc-rec-1k
kmalloc-rec-2k
kmalloc-rec-4k
kmalloc-rec-8k
kmalloc-rec-16k

I slightly favour the latter as it'll be easier to implement.  Something like

        static const char suffixes[3] = ' kM';
        int idx = 0;

        while (size > 1024) {
                size /= 1024;
                idx++;
        }

        sprintf("%d%c", size, suffices[idx]);