From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pekka Enberg Subject: Re: Mainline kernel OLTP performance update Date: Thu, 22 Jan 2009 11:15:07 +0200 Message-ID: <1232615707.14549.6.camel@penberg-laptop> References: <200901161503.13730.nickpiggin@yahoo.com.au> <20090115201210.ca1a9542.akpm@linux-foundation.org> <200901161746.25205.nickpiggin@yahoo.com.au> <20090116065546.GJ31013@parisc-linux.org> <1232092430.11429.52.camel@ymzhang> <87sknjeemn.fsf@basil.nowhere.org> <1232428583.11429.83.camel@ymzhang> <1232613395.11429.122.camel@ymzhang> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Christoph Lameter , Andi Kleen , Matthew Wilcox , Nick Piggin , Andrew Morton , netdev@vger.kernel.org, sfr@canb.auug.org.au, matthew.r.wilcox@intel.com, chinang.ma@intel.com, linux-kernel@vger.kernel.org, sharad.c.tripathi@intel.com, arjan@linux.intel.com, suresh.b.siddha@intel.com, harita.chilukuri@intel.com, douglas.w.styner@intel.com, peter.xihong.wang@intel.com, hubert.nueckel@intel.com, chris.mason@oracle.com, srostedt@redhat.com, linux-scsi@vger.kernel.org, andrew.vasquez@qlogic.com, anirban.chakraborty@qlogic.com To: "Zhang, Yanmin" Return-path: In-Reply-To: <1232613395.11429.122.camel@ymzhang> Sender: linux-scsi-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, 2009-01-22 at 16:36 +0800, Zhang, Yanmin wrote: > On Wed, 2009-01-21 at 18:58 -0500, Christoph Lameter wrote: > > On Tue, 20 Jan 2009, Zhang, Yanmin wrote: > >=20 > > > kmem_cache =EF=BB=BFskbuff_head_cache's object size is just 256, = so it shares the kmem_cache > > > with =EF=BB=BF:0000256. Their order is 1 which means every slab c= onsists of 2 physical pages. > >=20 > > That order can be changed. Try specifying slub_max_order=3D0 on the= kernel > > command line to force an order 0 alloc. > I tried =EF=BB=BFslub_max_order=3D0 and there is no improvement on th= is UDP-U-4k issue. > Both get_page_from_freelist and __free_pages_ok's cpu time are still = very high. >=20 > I checked my instrumentation in kernel and found it's caused by large= object allocation/free > whose size is more than PAGE_SIZE. Here its order is 1. >=20 > The right free callchain is __kfree_skb =3D> skb_release_all =3D> skb= _release_data. >=20 > So this case isn't the issue that batch of allocation/free might eras= e partial page > functionality. So is this the kfree(skb->head) in skb_release_data() or the put_page() calls in the same function in a loop? If it's the former, with big enough size passed to __alloc_skb(), the networking code might be taking a hit from the SLUB page allocator pass-through. Pekka -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html