> > At this point, I would be very interested in reviewing, correctness
> > testing on different configurations, and of course benchmarking.
>
> I haven't review this series so long time. but I've found one misterious
> shrink_slab() usage. can you please see my patch? (I will send it as
> another mail)
Plus, I have one question. upstream shrink_slab() calculation and your
calculation have bigger change rather than your patch description explained.
upstream:
shrink_slab()
lru_scanned max_pass
basic_scan_objects = 4 x ------------- x -----------------------------
lru_pages shrinker->seeks (default:2)
scan_objects = min(basic_scan_objects, max_pass * 2)
shrink_icache_memory()
sysctl_vfs_cache_pressure
max_pass = inodes_stat.nr_unused x --------------------------
100
That said, higher sysctl_vfs_cache_pressure makes higher slab reclaim.
In the other hand, your code:
shrinker_add_scan()
scanned objects
scan_objects = 4 x ------------- x ----------- x SHRINK_FACTOR x SHRINK_FACTOR
total ratio
shrink_icache_memory()
ratio = DEFAULT_SEEKS * sysctl_vfs_cache_pressure / 100
That said, higher sysctl_vfs_cache_pressure makes smaller slab reclaim.
So, I guess following change honorly refrect your original intention.
New calculation is,
shrinker_add_scan()
scanned
scan_objects = ------------- x objects x ratio
total
shrink_icache_memory()
ratio = DEFAULT_SEEKS * sysctl_vfs_cache_pressure / 100
This has the same behavior as upstream. because upstream's 4/shrinker->seeks = 2.
also the above has DEFAULT_SEEKS = SHRINK_FACTORx2.
===============
o move 'ratio' from denominator to numerator
o adapt kvm/mmu_shrink
o SHRINK_FACTOR / 2 (default seek) x 4 (unknown shrink slab modifier)
-> (SHRINK_FACTOR*2) == DEFAULT_SEEKS
---
arch/x86/kvm/mmu.c | 2 +-
mm/vmscan.c | 10 ++--------
2 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ae5a038..cea1e92 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2942,7 +2942,7 @@ static int mmu_shrink(struct shrinker *shrink,
}
shrinker_add_scan(&nr_to_scan, scanned, global, cache_count,
- DEFAULT_SEEKS*10);
+ DEFAULT_SEEKS/10);
done:
cache_count = shrinker_do_scan(&nr_to_scan, SHRINK_BATCH);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 89b593e..2d8e9ab 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -208,14 +208,8 @@ void shrinker_add_scan(unsigned long *dst,
{
unsigned long long delta;
- /*
- * The constant 4 comes from old code. Who knows why.
- * This could all use a good tune up with some decent
- * benchmarks and numbers.
- */
- delta = (unsigned long long)scanned * objects
- * SHRINK_FACTOR * SHRINK_FACTOR * 4UL;
- do_div(delta, (ratio * total + 1));
+ delta = (unsigned long long)scanned * objects * ratio;
+ do_div(delta, total+ 1);
/*
* Avoid risking looping forever due to too large nr value:
--
1.6.5.2
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