Messages in this thread | | | Date | Fri, 23 Jan 2009 08:52:27 +0200 | From | Pekka Enberg <> | Subject | Re: Mainline kernel OLTP performance update |
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Zhang, Yanmin wrote: >>>> 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. >> Do we know what kind of size is being passed to __alloc_skb() in this >> case? > In function __alloc_skb, original parameter size=4155, > SKB_DATA_ALIGN(size)=4224, sizeof(struct skb_shared_info)=472, so > __kmalloc_track_caller's parameter size=4696.
OK, so all allocations go straight to the page allocator.
> >> Maybe we want to do something like this. >> >> SLUB: revert page allocator pass-through > This patch amost fixes the netperf UDP-U-4k issue. > > #slabinfo -AD > Name Objects Alloc Free %Fast > :0000256 1658 70350463 70348946 99 99 > kmalloc-8192 31 70322309 70322293 99 99 > :0000168 2592 143154 140684 93 28 > :0004096 1456 91072 89644 99 96 > :0000192 3402 63838 60491 89 11 > :0000064 6177 49635 43743 98 77 > > So kmalloc-8192 appears. Without the patch, kmalloc-8192 hides. > kmalloc-8192's default order on my 8-core stoakley is 2.
Christoph, should we merge my patch as-is or do you have an alternative fix in mind? We could, of course, increase kmalloc() caches one level up to 8192 or higher.
> > 1) If I start CPU_NUM clients and servers, SLUB's result is about 2% better than SLQB's; > 2) If I start 1 clinet and 1 server, and bind them to different physical cpu, SLQB's result > is about 10% better than SLUB's. > > I don't know why there is still 10% difference with item 2). Maybe cachemiss causes it?
Maybe we can use the perfstat and/or kerneltop utilities of the new perf counters patch to diagnose this:
http://lkml.org/lkml/2009/1/21/273
And do oprofile, of course. Thanks!
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