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Date: Thu, 12 Feb 2009 13:22:33 +0800 From: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> To: Pekka Enberg <penberg@...helsinki.fi> Cc: Christoph Lameter <cl@...ux-foundation.org>, Andi Kleen <andi@...stfloor.org>, Matthew Wilcox <matthew@....cx>, Nick Piggin <nickpiggin@...oo.com.au>, Andrew Morton <akpm@...ux-foundation.org>, netdev@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>, matthew.r.wilcox@...el.com, chinang.ma@...el.com, linux-kernel@...r.kernel.org, sharad.c.tripathi@...el.com, arjan@...ux.intel.com, suresh.b.siddha@...el.com, harita.chilukuri@...el.com, douglas.w.styner@...el.com, peter.xihong.wang@...el.com, hubert.nueckel@...el.com, chris.mason@...cle.com, srostedt@...hat.com, linux-scsi@...r.kernel.org, andrew.vasquez@...gic.com, anirban.chakraborty@...gic.com, Ingo Molnar <mingo@...e.hu> Subject: Re: Mainline kernel OLTP performance update On Sat, 2009-01-24 at 09:36 +0200, Pekka Enberg wrote: > On Fri, 2009-01-23 at 10:22 -0500, Christoph Lameter wrote: > >> No there is another way. Increase the allocator order to 3 for the > >> kmalloc-8192 slab then multiple 8k blocks can be allocated from one of the > >> larger chunks of data gotten from the page allocator. That will allow slub > >> to do fast allocs. > > On Sat, Jan 24, 2009 at 4:55 AM, Zhang, Yanmin > <yanmin_zhang@...ux.intel.com> wrote: > > After I change kmalloc-8192/order to 3, the result(pinned netperf UDP-U-4k) > > difference between SLUB and SLQB becomes 1% which can be considered as fluctuation. > > Great. We should fix calculate_order() to be order 3 for kmalloc-8192. > Are you interested in doing that? Pekka, Sorry for the late update. The default order of kmalloc-8192 on 2*4 stoakley is really an issue of calculate_order. slab_size order name ------------------------------------------------- 4096 3 sgpool-128 8192 2 kmalloc-8192 16384 3 kmalloc-16384 kmalloc-8192's default order is smaller than sgpool-128's. On 4*4 tigerton machine, a similiar issue appears on another kmem_cache. Function calculate_order uses 'min_objects /= 2;' to shrink. Plus size calculation/checking in slab_order, sometimes above issue appear. Below patch against 2.6.29-rc2 fixes it. I checked the default orders of all kmem_cache and they don't become smaller than before. So the patch wouldn't hurt performance. Signed-off-by Zhang Yanmin <yanmin.zhang@...ux.intel.com> --- diff -Nraup linux-2.6.29-rc2/mm/slub.c linux-2.6.29-rc2_slubcalc_order/mm/slub.c --- linux-2.6.29-rc2/mm/slub.c 2009-02-11 00:49:48.000000000 -0500 +++ linux-2.6.29-rc2_slubcalc_order/mm/slub.c 2009-02-12 00:08:24.000000000 -0500 @@ -1856,6 +1856,7 @@ static inline int calculate_order(int si min_objects = slub_min_objects; if (!min_objects) min_objects = 4 * (fls(nr_cpu_ids) + 1); + min_objects = min(min_objects, (PAGE_SIZE << slub_max_order)/size); while (min_objects > 1) { fraction = 16; while (fraction >= 4) { @@ -1865,7 +1866,7 @@ static inline int calculate_order(int si return order; fraction /= 2; } - min_objects /= 2; + min_objects --; } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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