Messages in this thread Patch in this message | | | From | KOSAKI Motohiro <> | Subject | Re: VFS scalability git tree | Date | Sat, 24 Jul 2010 19:54:43 +0900 (JST) |
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> > 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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