Messages in this thread | | | Date | Fri, 4 May 2007 22:14:46 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [RFC 0/3] Slab Defrag / Slab Targeted Reclaim and general Slab API changes |
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On Sat, 5 May 2007, Eric Dumazet wrote:
> > C. Introduces a slab_ops structure that allows a slab user to provide > > operations on slabs. > > Could you please make it const ?
Sure. Done.
> > All of this is really not necessary since the compiler knows how to align > > structures and we should use this information instead of having the user > > specify an alignment. I would like to get rid of SLAB_HWCACHE_ALIGN > > and kmem_cache_create. Instead one would use the following macros (that > > then result in a call to __kmem_cache_create). > > Hum, the problem is the compiler sometimes doesnt know the target processor > alignment. > > Adding ____cacheline_aligned to 'struct ...' definitions might be overkill if > you compile a generic kernel and happens to boot a Pentium III with it.
Then add ___cacheline_aligned_in_smp or specify the alignment in the various other ways that exist. Practice is that most slabs specify SLAB_HWCACHE_ALIGN. So most slabs are cache aligned today.
> G. Being able to track the number of pages in a kmem_cache > > > If you look at fs/buffer.c, you'll notice the bh_accounting, recalc_bh_state() > that might be overkill for large SMP configurations, when the real concern is > to be able to limit the bh's not to exceed 10% of LOWMEM. > > Adding a callback in slab_ops to track total number of pages in use by a given > kmem_cache would be good.
Such functionality exists internal to SLUB and in the reporting tool. I can export that function if you need it.
> Same thing for fs/file_table.c : nr_file logic > (percpu_counter_dec()/percpu_counter_inc() for each file open/close) could be > simplified if we could just count the pages in use by filp_cachep kmem_cache. > The get_nr_files() thing is not worth the pain.
Sure. What exactly do you want? The absolute number of pages of memory that the slab is using?
kmem_cache_pages_in_use(struct kmem_cache *) ?
The call will not be too lightweight since we will have to loop over all nodes and add the counters in each per node struct for allocates slabs.
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